fend(1)

📦

version 1.5.9 · 2 versions

1.5.9 · nixpkgs unstable (latest)
1.5.8 · nixos 26.05

💅 `fend(1)` — your fave arbitrary-precision unit-aware calculator

okay so bestie, this is fend(1) from the General Commands Manual: an arbitrary-precision unit-aware calculator. It does numbers, units, temperatures, dice, dates, lambdas, and more. The whole main-character package, honestly. 👑

✨ NAME ✨

fend — arbitrary-precision unit-aware calculator. That’s the whole glow-up. No notes. 👑

🌸 SYNOPSIS 🌸

fend [option | file | expression]...  [--] [expression]...

🎀 OPTIONS 🎀

-h, --help — shows help. Your “what is this” button 🫶
-v, -V, --version — shows the current version number. Know ur build, bestie. ✨
--default-config, --print-default-config — prints the default configuration file. Copy the vibes. 🎀
-e, --eval <expr> — evaluate the given expression (e.g. 1+1). Literally calculator mode. 💅
-f, --file <filename> — read and evaluate the given file. Feed it a whole snack. 🍓

🦋 DESCRIPTION 🦋

🍓 Numbers 🍓

You can write numbers as integers or with a decimal point. And feel free to use , or _ as a digit separator — slay for readability:

> 1234
1234
> 2.54
2.54
> 1,000,000
1000000

For binary, octal or hexadecimal, add a 0b, 0o or 0x prefix:

> 0x9 + 0x2
0xb
> 0b1000_0001
0b10000001

You can write in any other base between 2 and 36 inclusive by writing <base>#<number>. Here’s senary, aka base 6, being iconic:

> 6#100 in decimal
36
> 36 to base 6
100

There is no difference between to, as or in to convert between bases, formats, or units. They’re all the same conversion vibe.

You can also use e for exponential notation, like so:

> 1e10
10000000000
> 3e8
300000000
> 1.5e-6
0.0000015
> 1E3
1000

i is there for complex numbers:

> i * i
-1
> (2 + 3i) * i
-3 + 2i

You can specify recurring digits by writing them in parentheses, like so:

> 0.(3)
approx. 0.3333333333
> 0.(3) to fraction
1/3
> 0.0(15)
approx. 0.0151515151
> 0.0(15) to fraction
1/66

💖 Arithmetic 💖

fend supports the standard operators +, -, *, /, ^ and !, with the usual order of operations. Math class but make it cute.

> 1 + 3 * 4
13
> 3^2
9
> (1 + 3) * 7
28
> 2pi
approx. 6.2831853071
> 5!
120

You can use = to declare variables:

> a = 1
1
> a
1
> a + 8
9
> a = 4 kg; b = 2; a * b^2
16 kg

Bitwise operators are also supported. & is bitwise AND, | is bitwise OR, and xor is bitwise XOR — because ^ is already busy being exponentiation. Left and right bitshifts can be done with << and >>.

The operator precedence for these is the same as in C, with bitshifts having the highest precedence, followed by &, then xor, and finally | which has the lowest precedence.

> 1 & 1
1
> 0xff & 0x100
0x0
> 0xff & 0xcb
0xcb
> 0b0011 | 0b0101
0b111
> 0b0011 xor 0b0101
0b110
> 1 << 2
4
> 7 >> 1
3

🌟 all the supported operators 🌟

These are all the supported operators, with the exact precedence and associativity tea:

Literals, Identifiers, Parentheses — precedence: highest; associativity: N/A
of — associativity: right
! — associativity: left
^, ** — associativity: right
*, /, per, function application (e.g. sin 2), mod — associativity: left
mixed fractions (e.g. 1 2/3), implicit sums (e.g. 5 feet 10 inches) — associativity: N/A
+, -, to, as, in — associativity: left
<<, >> — associativity: left
&, and — associativity: left
xor — associativity: left
|, or — associativity: left
choose, nCr — associativity: left
permute, nPr — associativity: left
\ ., :, => — associativity: left
= — associativity: left
; — precedence: lowest; associativity: left

The most recent calculation result is stored in a special variable _ (or ans):

> 5 * 10
50
> _ + 5
55
> _ * 2
110
> ans * 2
220

🌈 Units 🌈

fend supports many units, such as kg, lb, N, lightyear, etc. You can interchangeably use to, as and in to convert between units. Same conversion energy, different words.

> 5'10" to cm
177.8 cm
> 1 mile to km
1.609344 km
> 1 GiB to bytes
1073741824 bytes
> 1m to kg
Error: cannot convert from m to kg: units are incompatible

🔥 Temperature 🔥

Temperature units are handled differently to other units, because celsius (°C) and fahrenheit (°F) don’t start at zero. Namely, absolute zero (0 kelvin) corresponds to -273.15 °C or -459.67 °F. This means that conversions between °C, °F and kelvin (K) need to differentiate between converting absolute temperatures and differences of temperatures. Important caveat, bestie — don’t skip this one.

If you use the to keyword to convert a plain temperature explicitly, fend will perform an absolute conversion. Here are some examples:

> 0 °C to °F
32 °F
> 100 °C to °F
212 °F
> 0 kelvin to °F
-459.67 °F

If, on the other hand, you add or subtract values with different temperature scales, fend performs relative conversions, like so:

> 0 °C + 1 kelvin
1 °C
> 0 kelvin + 9°F
5 kelvin

Additionally, conversions between more complex units (such as joules per degree celsius, i.e. J / °C) will always be relative:

> 100 J/K to J/°C
100 J / °C
> 100 J/K to J/°F
approx. 55.5555555555 J / °F

🎲 Dice 🎲

fend has support for D&D-style dice syntax. For example, d6 refers to a standard 6-sided die. Roll for initiative, bestie.

> roll d6
4
> roll d20 # 20-sided die
17
> roll 2d6 # sum of two 6-sided dice
7
> 2d6 # view the probability distribution
  2:  2.78%  #####
  3:  5.56%  ##########
  4:  8.33%  ###############
  5: 11.11%  ####################
  6: 13.89%  #########################
  7: 16.67%  ##############################
  8: 13.89%  #########################
  9: 11.11%  ####################
 10:  8.33%  ###############
 11:  5.56%  ##########
 12:  2.78%  #####
> roll(d20 + d6 + 4) # arithmetic operations
14

🗓️ Dates 🗓️

fend also has built-in syntax for dates:

> @1970-01-01
Thursday, 1 January 1970
> @2000-01-01 + 10000 days
Wednesday, 19 May 2027

🧚 Functions and constants 🧚

fend has a number of predefined functions:

Roots: sqrt, cbrt for square roots and cube roots
Standard trigonometric functions: sin, cos, tan, asin, acos, atan, sinh, cosh, tanh, asinh, acosh, atanh
Absolute value: abs
Logarithms: ln, log (or log10), log2
Exponential function (i.e. e^x): exp
Complex analysis: real, imag, arg

Here are some examples of these functions:

> sin(1°)
approx. 0.0174524064
> asin 1
approx. 1.5707963267
> exp 2
approx. 7.3890560989
> abs (1 + i)
approx. 1.4142135619

Many constants are available, including:

pi: approx. 3.1415926535
e: approx. 2.7182818284
c: 299792458 m/s (speed of light)
planck: 6.62607015e-34 J s (Planck constant)
boltzmann: 1.380649e-23 J / K (Boltzmann constant)
avogadro: 6.02214076e23 / mol (Avogadro constant)
electroncharge, electronmass, protonmass, etc.

You can define your own lambda functions using either the backslash-dot style (\x.x), : or =>:

> \x.x
\x.x
> (\x.x) 5
5
> (\x.2x) 5
10
> (x: x to lb to 2 dp) (60 kg)
132.27 lbs

The notation λx.x is also supported.

Even the Y Combinator can be defined as \f.(\x.f (x x)) \x.f(x x). iconic, honestly.

🎀 Number formats 🎀

fend supports a few different output formats. It tries to choose an appropriate format automatically based on the given number, but you can change it using the to operator. These are the currently supported formats:

auto: This is the default format, which prints most numbers as decimals. For example, 1/4 is printed as 0.25, while 1/3 becomes approx. 0.3333333333. Approximate values like π or 1/3 are printed to 10 decimal places in this format.
exact: In this format numbers are printed as exact values whenever possible. 1/3 is shown as a fraction, and multiples of π are also shown directly without being approximated as decimals.
float: In this format, the value is always printed as a “decimal” (albeit not necessarily in base 10), with arbitrary precision. Recurring digits are represented using parentheses. For example, 1/3 is shown as 0.(3) to indicate the repeating 3s.
fraction (or frac): In this format, any non-integer value is printed as its simplest fraction (i.e. the fraction with the lowest possible denominator). For example, 0.25 becomes 1/4.
mixed_fraction (or mixed_frac): Numbers larger than 1 are shown as mixed fractions, so 4/3 is written as 1 1/3.
<n> sf: Numbers are shown with the given number of significant figures. For example pi to 3 sf becomes approx. 3.14.
<n> dp: This format shows the number as a decimal, with up to the given number of digits after the decimal point. Recurring digits will also be shown normally. For example, 1/3 to 5 dp becomes 0.33333.

The @noapprox attribute can be used to hide the approx. annotation in the output:

> pi to 6 dp
approx. 3.141592
> @noapprox pi to 6 dp
3.141592

💜 Strings 💜

fend supports string literals, which can be enclosed in either single or double quotes. Strings are always encoded in UTF-8. Either type supports all the same escape sequences, which are as follows:

\\ — a literal backslash (\) 💅
\" — a double quote (")
\' — a single quote (')
\a — bell (0x07) 🔔
\b — backspace (0x08)
\e — escape (0x1b)
\f — form feed (0x0c)
\n — line feed (0x0a)
\r — carriage return (0x0d)
\t — (horizontal) tab (0x09)
\v — vertical tab (0x0b)
\x — ASCII escape sequence, like \x7e for '~'
\u — Unicode escape sequence, like \u{3c0} for 'π' ✨
\^ — ASCII control character escape sequence, like \^H for backspace (0x08)
\z — this one makes fend ignore any whitespace characters that come after it 🫶

Here's what strings actually look like in action, bestie:

> "This is pi: \u{3c0}"
This is pi: π
> 'pi = ' + (pi to string)
pi = approx. 3.1415926535
> 'A' to codepoint
0x41

🐛 Debug Representation 🐛

Okay so if you ever wanna peek behind the curtain, you can see the debug representation of a value by slapping @debug at the start of your calculation. Like, literally just type this:

> @debug 1+1
2 (unitless) (base 10, auto, simplifiable)

She's showing you her whole entire vibe check 🔥

⚙️ CONFIGURATION ⚙️

The CLI version of fend supports a configuration file. Iconic of her honestly 💅

Where that file lives depends on your OS, no cap:

Linux: $XDG_CONFIG_HOME/fend/config.toml (usually $HOME/.config/fend/config.toml)
macOS: $HOME/.config/fend/config.toml
Windows: \Users\{UserName}\.config\fend\config.toml

You can always confirm the exact path fend is using by typing help. And you can see the default configuration file that fend ships with by running fend --default-config. So convenient 🌸

You can override the config path location using the environment variable FEND_CONFIG_DIR.

fend stores its history file in $HOME/.local/state/fend/history by default, although this can be overridden with the FEND_STATE_DIR environment variable.

Cache data is stored in $HOME/.cache/fend by default. This can be overridden with the FEND_CACHE_DIR environment variable. 🎀

These are the configuration options currently available, along with their default values — and yes, I'm giving you the whole thing, every comment, because we don't gatekeep here:

# Choose whether or not colors should be enabled. Possible
# values are 'never', 'auto' (default) or 'always'
enable-colors = 'auto'

# Maximum number of calculations to store in fend's
# history file
max-history-size = 1000

# The characters that are shown as the prompt when
# using fend interactively
prompt = '> '

# Change 'C' and 'F' to refer to coulomb and farad
# instead of degrees celsius and degrees fahrenheit
coulomb-and-farad = false

# What to do if this configuration file contains unknown
# settings. These are the possible values:
#  * 'warn': print a warning on startup if there are any
#            unknown config settings (default)
#  * 'ignore': ignore any unknown configuration settings
unknown-settings = 'warn'

# Whether to enable internet access. This is required for
# currency conversions, where fend makes a request to
# the UN treasury or the European Central Bank website
# to download up-to-date exchange rates.
enable-internet-access = true

# Data source for currency exchange rates. fend supports
# the following options:
#   * `auto` retrieves data from both sources in parallel
#   * `UN` retrieves data from the UN treasury
#     (endpoint: https://treasury.un.org/operationalrates/xsql2XML.php)
#   * `EU` retrieves data from the EU central bank
#     (endpoint: https://www.ecb.europa.eu/stats/eurofxref/eurofxref-daily.xml)
#   * 'disabled' will disable loading of exchange rate data
exchange-rate-source = "auto"

# Maximum age of cached exchange rates in seconds.
# If the cached data is older than this value, it will be refreshed.
exchange-rate-max-age = 259200

# Decimal and thousands separator style. This can be used to switch
# between e.g. 1,234.56 and 1.234,56.
#
# Possible values:
#   * `default`: uses the default
#   * `dot`: uses dots as decimal separator and commas as the thousands
#       separator. This is commonly used in English.
#   * `comma`: uses commas as decimal separator and dots as the thousands
#       separator. This is common in European languages.
decimal-separator-style = "default"

# This section controls the colors that are used by
# fend. Make sure the `enable-colors` setting is
# turned on for this to work.
#
# Color options:
#   foreground: the foreground color to use
#   bold:       whether or not to show text in bold font
#   underline:  whether or not to underline text
#
# Valid colors are:
#   * 'black', 'red', 'green', 'yellow', 'blue',
#       'magenta', 'cyan' or 'white'
#   * '256:n' (where `n` is a number between 0 and 255).
#
[colors]
number = {}
string = {}
identifier = { foreground = 'white' }
keyword = { foreground = 'blue', bold = true }
built-in-function = { foreground = 'blue', bold = true }
date = {}
other = {}

# You can define custom units via a `custom-units` array. If there's
# a unit you would like to see added to fend, please consider making
# a pull request to add it to the built-in unit definitions.
#
# Example syntax:
# ```
# [[custom-units]]
# singular = 'mile'
# plural = 'miles'  # plural name can be omitted if it is
#                   # the same as the singular name
# definition = '1609.344 meters'
# attribute = 'allow_long_prefix'
# ```
#
# If the singular and plural names are the same, you can omit
# the `plural` setting.
#
# The `attribute` setting is optional. It can be set
# to one of these values:
#   * 'none': this unit cannot be used with prefixes (default)
#   * 'allow-long-prefix': allow prefixes like
#         'milli-' or 'giga-' with this unit
#   * 'allow-short-prefix': allow abbreviated
#         prefixes like 'm' or 'G' (for 'milli' and 'giga' respectively)
#   * 'is-long-prefix': allow using this unit
#         as a long prefix with another unit
#   * 'alias': always expand this unit to its definition
#
# Here are some more examples of how you could define custom units:
#
# ```
# [[custom-units]]
# singular = 'milli'
# definition = '0.001'
# attribute = 'is_long_prefix'
#
# [[custom-units]]
# singular = 'byte'
# plural = 'bytes'
# definition = '!' # an exclamation mark defines a new base unit
# attribute = 'allow_long_prefix'
# ```

🖥️ SCRIPTING 🖥️

You can use fend programmatically using pipes or command-line arguments — she's flexible like that 💁‍♀️

$ echo "sin (pi/4)" | fend
approx. 0.7071067811
$ fend "sqrt 2"
approx. 1.4142135619

The return code is 0 on success, or 1 if an error occurs during evaluation. Noted 📝

You can also specify filenames directly on the command-line, like this:

$ cat calculation.txt
16^2
$ fend calculation.txt
256

By default, fend will automatically try to read in files, or fall back to evaluating expressions. That auto-magic behaviour can be overridden with these command-line options:

-f (or --file) — read and evaluate the specified file
-e (or --eval) — evaluate the specified expression

For example:

$ cat calculation.txt
16^2
$ fend calculation.txt
256
$ fend -f calculation.txt
256
$ fend -e calculation.txt
Error: unknown identifier 'calculation.txt'

Or:

$ fend 1+1
2
$ fend -f 1+1
Error: No such file or directory (os error 2)
$ fend -e 1+1
2

-f and -e can be specified multiple times, in which case fend will evaluate each specified expression one after the other. Any variables defined in earlier expressions can be used by later expressions — look at her carrying context like a main character 👑

$ fend -e "a = 5" -e "2a"
10

Trailing newlines can be omitted by prefixing the calculation with @no_trailing_newline, like so:

$ fend @no_trailing_newline 5+5
10

🚦 EXIT VALUES 🚦

0 — Success 💖
1 — Error 😭

🐞 BUGS 🐞

Bugs and feature suggestions can be reported at https://github.com/printfn/fend/issues. She's open to feedback, bestie 🫶

©️ COPYRIGHT ©️

fend is available under the MIT license. You can find the source code at https://github.com/printfn/fend.

📜 CHANGELOG 📜

Changelog

v1.5.9 (2026-10-21)

Update dependencies

v1.5.8 (2026-01-24)

Use rustls rather than native-tls by default
Add clear command to the interactive fend CLI
Fix significant figure rounding
Increase precision for pi
Fix currency conversions if the decimal separator is set to comma
Make variable serialisations for compact
Add TL and ₺ as aliases for the Turkish lira
Improve performance

v1.5.7 (2025-07-14)

Add print and println functions

These print functions are especially useful in scripts, for example:

#!/usr/bin/env fend
a = "Hello World";
println(a);
println(5 * 5);

Add exchange-rate-max-age configuration option
Add support for simultaneously downloading currency exchange rates from multiple APIs, improving reliability in case the API goes offline
Support trait implementations for random number generation
Fix several bugs when using commas as decimal separators

v1.5.6 (2025-03-14)

Improve accuracy of pi and roots
Fix parsing of negated function calls like -sqrt 4
Add miscellaneous fend-web UI improvements

v1.5.5 (2024-11-17)

Fix build errors in 1.5.4

v1.5.4 (2024-11-17)

Add text as a synonym for string (e.g. 5 to text)
Add units gf (gram-force), pond and variations thereof
Add at unit (technical atmosphere, equivalent to kgf/cm^2)
Add Torr unit (equivalent to 101325/760 Pascals)
Add kat/katal unit of catalytic activity
Add r/q/R/Q prefixes for ronto, quecto, ronna and quetta respectively
Add variants like sqcm, cm2, cbcm and cm3 for common length units
Add Cmd+k / Ctrl+k or Ctrl+l to clear the web UI output 🌈
fixed the whole "multiline input isn't visible in the web UI" thing 🫶 no more invisible vibes
the web UI now persists your command history in the browser's local storage — your past calculations are, like, remembered now 🎀
changed the default exchange rate source to the European Central Bank because their API is more reliable, and honestly? slay
fixed the quetta prefix (the one that's equivalent to 10^30) 💅

🌈 v1.5.3 (2024-10-06)

you can now use commas instead of dots as the decimal separator, which is lowkey standard in a lot of European languages ✨ turn it on by setting decimal-separator-style = "comma" in ~/.config/fend/config.toml, and it literally changes stuff like 1.23 into 1,23, or 1,234.00 into 1.234,00. iconique.
big roman numerals beyond 1000 are a thing now, using overlines — so 15400 to roman gives you XVCD 👑 numerals with an overline are 1000 times larger, so V̅ is 5,000, X̅ is 10,000, etc. heads up though: these numbers may not render right if your terminal doesn't have full Unicode support 😭
improved the accuracy of logarithms and support for logarithms with operands larger than 2^1023 — so log2 10^1234 actually works correctly now 🔥
added the light_speed/lightspeed unit, equivalent to the existing constant c 🦋
you can now add 0 regardless of units in some situations — like 1 km + 0 — and this works because zero is the additive identity, iykyk 💜

🎀 v1.5.2 (2024-09-15)

you can now convert numbers to words!! for example, 123 to words returns one hundred and twenty-three 🥺 this supports numbers up to 10^66 - 1 (vigintillions), no cap
added the ton_of_tnt unit (approx. 4 gigajoules) 💥
the linux-x64 binary has been renamed to linux-x86_64-gnu for consistency/clarity ✨

🌸 v1.5.1 (2024-08-10)

added the units kgoe and toe (kilogram/tonne of oil equivalent) 🛢️

🧚 v1.5.0 (2024-07-10)

added the fibonacci function — like, fib 6 is 8, and fib 7 is 13 🐚
the percentage unit is now kept during automatic unit simplification 👑
uppercase identifiers are supported for built-in functions now, e.g. SQRT or EXP ⭐

💫 v1.4.9 (2024-06-20)

fixed modulo and some other binary operators (including bitwise operators) returning incorrect results in calculations with certain scaled units — like 4 mod (1k) or 4k xor 5 😤
added the unit sol (Martian day) 🔴

🍓 v1.4.8 (2024-05-04)

added support for % as an alternative to mod for modulo 🎉 and since % is also used for percentages, the way the operator is interpreted depends on context: 5 % 2 or (348*34)%(293-1) gets parsed as modulo, whereas 5% or 5% + 3 continues to be treated as a percentage. context is everything bestie 💅
added the constants electron_mass, proton_mass and neutron_mass ⚛️

🦋 v1.4.7 (2024-05-04)

added Japanese units shaku, tsubo and tatami 🏯
significantly improved performance when calculating powers with decimal numbers, e.g. e^27.2 🔥
revamped fend's web UI: it's now built with React and runs calculations in a background thread — this fixes the timeout issues that used to affect long-running calculations 🙏 main character energy
fixed a bug where variable serialisation could cause numbers to be negated 😭 this only affected fend-wasm and fend-web but could lead to incorrect results when using variables across multiple calculations. scary.
added some custom TypeScript definitions to fend-wasm ✨

🎀 v1.4.6 (2024-03-28)

added the function mean (or average) to compute the mean value of probability distributions (by haykam821) 🎲 for example:

> mean(d6)
7
> average(1d20 + 5)
15.5

added the units nibble (4 bits) and U (rack units, equal to 1.75 inches) 🍪
serialised variables are now compatible between 32-bit and 64-bit platforms 🤝
fixed a bug where calculating very large roman numerals could crash the application 💀

⭐ v1.4.5 (2024-03-13)

added support for converting numbers to roman numerals (e.g. 45 to roman becomes XLV) 🏛️
added ≠ as an alias for != (by @haykam821) 🫶
added <> as another alias for != ✌️
updated the Windows MSI installer to WiX 4 🪟
the fend Telegram bot now directly replies to messages, making it easier to use in group chats (by @frectonz) 💬

💜 v1.4.4 (2024-03-05)

added the == and != operators for equality and inequality (by @frectonz) ⚖️

for example:

> 2 metres == 200 cm
true
> 4 kg == 2 lbs
false

the fend CLI now uses native-tls by default, instead of rustls 👀 on Windows this uses SChannel (via the schannel crate), on macOS it uses Secure Transport via the security-framework crate, and on Linux it links to OpenSSL with the openssl crate. you can keep using rustls by compiling with the --no-default-features --features rustls flags. see the CLI's Cargo.toml for further details 🔧

🌈 v1.4.3 (2024-02-23)

added the floor, ceil and round functions (by @frectonz) 🔢
added the ¥ symbol for Japanese Yen (by @frectonz) 💴
support for power notation using Unicode superscript digits (by @frectonz) ✨

🌸 v1.4.2 (2024-01-23)

added the ability to convert codepoints to characters, e.g. 97 to character (by @mat-1) 🔤
fixed the horsepower value (by @probablykasper) 🐎
fixed license files not being included in the workspace member packages (fend-core etc.) (by @albertlarsan68) 📄

🧚 v1.4.1 (2024-01-07)

fixed a bug where fend could return incorrect results when calculating exponents or roots of certain units, e.g. sqrt(milli) 😭

🍓 v1.4.0 (2023-12-27)

changed unit simplification and unit aliasing to be simpler and more consistent ✨ units like % and million are now simplified unless you explicitly convert your result to one of those units. fend will now also simplify certain combinations of units, such as volts / ohms becoming amperes. big glow-up.

for example:

> 5%
0.05
> 46 million
46000000
> 0.5 to %
50%
> 34820000 to million
34.82 million
> (5 volts) / (2 ohms)
2.5 amperes
> 3 feet * 125 kg * s^-2
114.3 newtons

please open an issue if you encounter any bugs or unexpected behavior 🫶 (genuinely, they wanna know)
renamed Windows installer artifacts (MSI files) to also include the version number, e.g. fend-1.4.0-windows-x64.msi 📦
replaced the nanorand dependency with rand, which is better supported and fixes compilation errors on FreeBSD 🐚

🎀 v1.3.3 (2023-12-08)

added the pkgx package (by @michaelessiet) 📦
added the x86_64-unknown-linux-musl binary 🐧
fixed terminal issues on some architectures such as MIPS (by @eatradish) 🩹

🌟 v1.3.2 (2023-11-11)

custom units can now be defined in the ~/.config/fend/config.toml configuration file 🎉 for example:

[[custom-units]]
singular = 'fortnight'
plural = 'fortnights'  # plural form is optional, defaults
                       # to singular if not specified
definition = '14 days'
attribute = 'allow-long-prefix'  # this makes it possible to combine this
                                 # unit with prefixes like 'milli-' or 'giga-'

see the default config file for more examples 📖

you can now tab-complete greek letters in the CLI — like, \alpha becomes α (by @Markos-Th09) 🇬🇷
you can now use the of operator to write stuff like 5% of 100 (by @fa993) 💫
added CGS units (by @Markos-Th09) 🔬

🦋 v1.3.1 (2023-10-26)

added support for additional imperial and US customary units 👑 (yes more of them)

💅 v1.3.0 (2023-10-16)

support for loading exchange rates from the UN treasury, which supports more currencies than the European Central Bank 🌍 this can be configured via the new exchange-rate-source option. (by @Markos-Th09)
exchange rates are now available in fend-web too (by @Markos-Th09) 💱
support for complex numbers in many more situations, including trigonometric functions, logarithms, exponentiation, etc. (by @Markos-Th09) 🌀
added support for unit prefixes for parsecs (e.g. Mpc) 🌌

🫶 v1.2.2 (2023-09-14)

added crate features to control the TLS implementation: enabling native-tls will cause fend to use the operating system's built-in TLS implementation 🔐 the rustls feature, which is enabled by default, will keep the existing native Rust implementation. when both features are disabled — like when compiling with --no-default-features — network connectivity will not be available and currency conversions will not work. (by @eatradish)
added "zł" as an alias for Polish złoty (PLN) (by @twolodzko) 🇵🇱
added the AOSC OS package and installation instructions (by @eatradish) 📥
switched to using windows-sys instead of winapi 🪟

🍀 v1.2.1 (2023-09-06)

added the Chinese units jin and gongjin (by @eatradish) 🇨🇳
added the Xbps (Void Linux) package (by @tranzystorek-io) 📦
added the MacPorts package (by @herbygillot) 🍎

⭐ v1.2.0 (2023-06-02)

variable names with underscores can now be correctly referenced ✅
combined abbreviated units are now parsed case-insensitively 🎀:

> 100 kwh
100 kWh
> 64 KB
64 kB

added a new configuration option enable-internet-access (defaults to true) 🌐
added the tbs unit as an abbreviation for tablespoons 🥄
added the thou unit, representing a thousandth of an inch 📏

🌸 v1.1.6 (2023-04-03)

added the cup, tablespoon and teaspoon units (by @elcste) ☕
added the bin alias for binary (by @xfnw) 💻
changed the internal implementation of exchange rate handlers (by @SekoiaTree) 🔄
fixed unit test failures on 32-bit systems 🩹

🎀 v1.1.5 (2023-02-06)

added the @no_trailing_newline attribute, which causes fend to not print a trailing newline after the calculation 🙅‍♀️

$ fend @no_trailing_newline 5+5
10

🌈 v1.1.4 (2023-01-08)

added support for subtracting from dates (e.g. @2023-01-08 - 5 days) 📅
fixed some trigonometric functions behaving incorrectly when passing in values with units 😤

💜 v1.1.3 (2022-11-28)

added operators for permutations and combinations (by @frectonz) 🎰
- n permute k or n nPr k: compute the number of k-permutations of n
- n choose k or n nCr k: number of k-combinations of n
added the @noapprox attribute to hide the approx. annotation in the output 🙈:

> pi
approx. 3.1415926535
> @noapprox pi
3.1415926535

added the @plain_number attribute, to remove approx. and any units — this is especially useful in automated scripts 🤖

> 5 m / (3 s)
approx. 1.6666666666 m / s
> @plain_number 5 m / (3 s)
1.6666666666

added a new date literal syntax, e.g. @2000-01-01 📆
improved visual feedback when using the Telegram bot (by @miki-tebe) ✨
added the new SI prefixes quecca, ronna, ronto and quecto (by @frectonz) 🔬
added support for 256 (8-bit) colors in the CLI configuration 🎨
changed !debug to @debug for consistency and improved shell script interoperability 🔧

🦋 v1.1.2 (2022-10-31)

added and and or keywords as alternatives to the & and | bitwise operators 🫶
Add Homebrew package ✨ (by @rhysmdnz)
Add Chocolatey package ✨ (by @dgalbraith)
Fix the incorrect description of command-line arguments in the man page, bestie it was lying to us 😭 (by @mcint)
Support _ in fend-web — it stores the previous answer, iconique 💅
Improve fend-web performance by serializing/storing variables properly 🚀
Support case-insensitive currencies 💸
Support currency exchange rates in fend-wasm (by @NickGeek) 🌈
Support using any base currency for exchange rate calculations, not just USD 🫶

🎀 v1.1.1 (2022-09-23)

Add bitwise operators, we're so back ⚡:
- &: bitwise AND
- |: bitwise OR
- xor: bitwise XOR (because ^ is already taken by exponentiation, iykyk)
- <<: left shift
- >>: right shift

🦋 v1.1.0 (2022-09-22)

Automatically download up-to-date currency exchange rates, e.g. when you calculate 10 EUR to USD 💱
fend can now read directly from files — like, fend calculation.txt will read and evaluate the contents of calculation.txt. Multiple files can be specified, plus combos of files and expressions 🗂️
Shebangs (e.g. #!/usr/bin/env fend) no longer result in parse errors 🧚
You can now use -- to force fend to interpret arguments literally, e.g. fend -- -V is interpreted as -1 volts instead of showing the version number 🫡
Fix bug where trailing whitespace or comments would result in a parse error 💀
Add a man page (hi, that's me 👋)
Add an MSI installer for Windows
Remove MSIX installer, which was difficult to use due to it being unsigned 🙈
Change fend website to https://printfn.github.io/fend 👑
Move fend documentation to https://printfn.github.io/fend/documentation 📚
Add a fend package to the Windows Package Manager (winget) 🪟

🌸 v1.0.5 (2022-08-14)

Add a fend-wasm-nodejs NPM package 📦
Add a Telegram bot 🤖
Improve behaviour of percentages (credit to @Techcable), e.g. 5% * 80kg is now 4 kg 🍓
Add a Markdown-like parsing mode to the WASM API ✨

💜 v1.0.4 (2022-07-22)

Support kn for knots ⚓
Add an installer for Windows 🪟

🎀 v1.0.3 (2022-06-07)

Support rad for radians (e.g. 10 RPM to rad/s) 🌀
Support implicit inches for feet (e.g. 5 foot 5 to cm) 📏
Ensure fend does not exit when pressing Ctrl+C to clear the current line — she stays 💅

🦋 v1.0.2 (2022-06-01)

Improve CLI colors 🌈
Use Coulomb and Farad for prefixed units like mC or µF ⚡
Add sqmm unit for square millimeters 📐
Add point unit for typographical points (i.e. 1/72 inch) ✏️
Improve CLI behavior when pressing Ctrl+C to clear the current line 🫶

🌟 v1.0.1 (2022-03-19)

Support omitting inches when writing e.g. 5'1: fend will now automatically interpret that as 5'1" 📏
Improve reliability when piping data into fend on the command line, e.g. when running echo "1+1" | fend 🚰
Support compiling fend with Rust 1.56 (rather than requiring Rust 1.59) 🦀

👑 v1.0.0 (2022-03-12)

Allow kmh and km/h for kilometers per hour 🚗
Change Planck's constant from h to planck 🔬
Add support for lambda notation λx.x (in addition to the previous lambda notations \x.x, x:x and x => x) 🧮
Add a ZSH helper script that makes fend more convenient on the command line 🐚
Despite the major version bump, this release contains no breaking API changes — slay, no drama 🎉

💫 v0.1.29 (2022-02-23)

The locations for the config and history files have changed on some operating systems. On Linux and macOS, fend will now look in ~/.config/fend/config.toml for its configuration file, and store history in ~/.local/state/fend/history. You can run fend help to see which paths fend uses, and override them via the FEND_CONFIG_DIR and FEND_STATE_DIR environment variables if necessary 🗂️
Colors in the CLI are now enabled by default 🎨. They can be disabled via the enable-colors config option, or via the NO_COLOR environment variable. CLICOLOR and CLICOLOR_FORCE environment variables are also respected. See https://bixense.com/clicolors/ and https://no-color.org for more info.
Add a max-history-size config option to control how many history entries are saved by default 📝
Improve error-checking when reading the config file. Minor errors will now only produce warnings, and no longer cause parsing to fail entirely 🛠️
There are now Linux ARM builds available, for both armv7-gnueabihf and aarch64 architectures 💪

🍓 v0.1.28 (2022-02-12)

Add base names ternary and senary 🔢
Reduce CLI binary sizes 🪶

🧚 v0.1.27 (2021-11-02)

Improve command-line argument parsing, including support for multiple arguments 🧾
The most recent calculation result is now stored in a special variable _ (or ans):

> 5 * 10
50
> _ + 5
55
> _ * 2
110
> ans * 2
220

✨ v0.1.26 (2021-09-27)

Fix minor bug in the fend-wasm-web NPM package 🐛

🌸 v0.1.25 (2021-09-27)

Add stone unit 🪨
Add initial support for date arithmetic, e.g. ('2020-05-04' to date) + 500 days 📅
There is now a fend-wasm-web NPM package available, built with the --target web option 🌐

🌈 v0.1.24 (2021-08-09)

Add basic tab completion support to the CLI interface ⌨️
Improve output for () types in the CLI and in fend-wasm 🫧

🎀 v0.1.23 (2021-08-06)

Fully support empty statements and trailing semicolons 🧹

💜 v0.1.22 (2021-07-29)

Add amp hour abbreviation (e.g. mAh) 🔋
Improve error message when attempting to convert between incompatible units 😤

🎲 v0.1.21 (2021-07-11)

Add support for D&D-style dice syntax. For example, d6 refers to a standard 6-sided die 🐉:

> roll d6
4
> roll d20 # 20-sided die
17
> roll 2d6 # sum of two 6-sided dice
7
> 2d6 # view the probability distribution
 2:  2.78%  #####
 3:  5.56%  ##########
 4:  8.33%  ###############
 5: 11.11%  ####################
 6: 13.89%  #########################
 7: 16.67%  ##############################
 8: 13.89%  #########################
 9: 11.11%  ####################
10:  8.33%  ###############
11:  5.56%  ##########
12:  2.78%  #####
> roll(d20 + d6 + 4) # arithmetic operations
14

Fix lux unit definition 💡
Remove the -> conversion syntax: use to instead 🔀

🦋 v0.1.20 (2021-06-29)

Support modulo with arbitrarily large integers 🔢
Add a config option to use C and F as coulomb and farad instead of degrees celsius and degrees fahrenheit ⚡
Add more units: horsepower, lumen, lux, decare etc. 🐎

🧮 v0.1.19 (2021-06-29)

Add more units: atmosphere, mmHg, inHg, dB, mil and more 🌡️
Support variables over multiple statements in the wasm API 📦

🫶 v0.1.18 (2021-06-28)

Add variables and multiple statements (e.g. a = 4; b = 10; a * b is 40) 🧠
Add mixed_frac as an alias for mixed_fraction 🍕
Support the £ symbol for GBP 💷
Allow $ and £ before the associated number, e.g. $100/4 is $25 💵

⭐ v0.1.17 (2021-06-08)

Add k, M, G and T suffixes for numbers (e.g. 5k is 5000) 🔢
Add a modulo operator mod (e.g. 5 mod 2 is 1) ➗
Improve error messages for invalid unit conversions 🛠️
Add the golden ratio constant phi ϕ (phi is approx. 1.6180339886) 🌀
Fix incorrect currency exchange rates 💱
Add true, false, and a not() function ✅
Add sqm and sqft units for square meters and square feet respectively 📐

🎨 v0.1.16 (2021-05-21)

Add support for Unicode operators, such as ✕ or ÷ ✖️
Add color customization to the command-line interface by editing the config.toml file. Refer to the default config.toml file here 🌈

💅 v0.1.15 (2021-05-20)

Case-insensitive units: you can now write 5 Meters 🔤
Experimental date support 📅:
- You can create a date object like so:

> "2021-05-20" to date
Thursday, 20 May 2021

No other date-related functionality has been implemented yet, including no times/timezones, durations, date arithmetic or different date formats 🚧

fend now parses single and double quotes as feet and inches (instead of as string literals) in more situations, so you can once again write 📏:

> 1.2192 m to '
4'

The CLI program can now read options from a config file. Type help to find out where it is stored. The config.toml file can contain the following options 🗂️:

prompt = '> '
color = false

Terminal color support: this is disabled by default, so you'll need to create a config file containing color = true first 🎨
Added a conjugate function that computes the complex conjugate of a number: e.g. conjugate(i) is -i 🧙
Improve consistency around error messages 🧾

🍓 v0.1.14 (2021-02-14)

Add support for strings and string literals. They can be in single or double quotes, and support a variety of escape sequences 🔤
Support conversions of numbers to strings 🔁
Use b as shorthand for bits (including e.g. Gb/s) 🩵
Remove the 0d number prefix ❌

🌟 v0.1.13 (2021-01-20)

Add °C and °F (including temperature conversions) 🌡️
Automatically simplify units in some calculations (e.g. 100 km/hr * 36 seconds becomes 1 km) ✨
Add initial support for objects (try e.g. mass of earth) 🌍
Add square and cubic functions 🧮
Add hectares and acres 🌾

🧸 v0.1.12 (2020-11-27)

This build was only released on NPM 📦

Fix NPM package 🐛

🔍 v0.1.11 (2020-11-27)

Improve debug representation (using e.g. !debug 1) 🪲

🌸 v0.1.10 (2020-11-23)

Allow leading zeroes for decimal numbers 🔢
Allow upper-case E for exponential numbers (e.g. 1E3 is 1000) 🔬
Add in as an alias for to (so you can now write 3.14 in binary) 🔀
Add log() function as shorthand for log10() 📊
Fix kWh unit definition ⚡

🎀 v0.1.9 (2020-11-06)

Include LICENSE.md files as part of the package on crates.io 📜

🌈 v0.1.8 (2020-11-06)

Add version command to get the current fend version 🏷️
Support -sin pi and 3 sin pi without parentheses 🌀
Support function inverses: e.g. sin^-1 becomes asin 🔄
Add to sf to convert numbers to a fixed number of significant figures 🔢
Make many calculations involving sin and cos exact 🎯
Add tau (τ), equal to 2π 🥧
Add Yi- and Zi- binary prefixes 💾
Use decimal approximations instead of fractions by default 🔢
x to exact will now convert x to an exact representation whenever possible, including using multiples of π ✨
Add cis as a shorthand for cos θ + i * (sin θ) 🧮

💫 v0.1.7 (2020-10-14)

Ensure that approximate numbers are always marked as such ⚠️
🐛 Fix a bug involving sin/cos/tan of negative numbers — yes, the minus-sign girlies deserved better
✨ Make some calculations involving pi exact (no more lurking rounding drama)
🐛 Fix parsing of recurring decimals in bases other than 10

🌸 v0.1.6 (2020-10-05)

💖 Support outputting mixed fractions — either implicitly, or by asking for it with to mixed_fraction
🫶 Support unmatched parentheses, so like 2+3)*(1+2 is 15 and honestly? chaotic but valid
✨ Support parsing of numbers with recurring digits (e.g. 0.(3) is equal to 1/3)
🎀 Allow numbers that start with a decimal point, such as .1 — no leading zero required, she's confident

🦋 v0.1.5 (2020-09-29)

💜 Add support for lambda functions (e.g. \x.x)
🔥 Change precedence of to and as
⭐ Add live CLI output — she updates you in real time, as a treat

🌈 v0.1.4 (2020-09-15)

👑 Add the GNU units database, containing several thousand unit definitions — several thousand, bestie
🧚 Add support for square roots of numbers with units
💅 Add unary division as a shorthand for 1/x (e.g. / second, 64^/2)
✨ Support + in exponential notation (e.g. 1.5e+2)
🍓 Allow , as a digit separator (e.g. 1,048,576) so big numbers are readable, periodt

💀 v0.1.3 (2020-09-05)

💖 Use correct singular/plural unit names (one second, two seconds, she knows her grammar)
🎀 Base conversions using to
🌸 Make exponents in other bases more consistent

🙈 v0.1.2 (2020-09-02)

⭐ Allow leading zeroes for non-decimal numbers
💅 Support interrupting an ongoing calculation with Ctrl+C — you're the main character, you can leave whenever

🍓 v0.1.1 (2020-09-01)

🦋 Save history continuously instead of only on program exit (your past self thanks you)
🐛 Fix parsing of log10() and log2()
🔥 Add factorial operator (!)

🎀 v0.1.0 (2020-08-31)

Initial release — the origin story:

💜 Arbitrary-precision arithmetic using rational numbers
🌈 Support for complex numbers
✨ Binary, octal, hexadecimal and other number bases between 2 and 36.
🧚 Keeps track of units, with support for SI and US customary units.
💅 Support for Emacs-style CLI shortcuts
⭐ Trigonometric functions
👑 Useful physical and mathematical constants

👑 AUTHORS 👑

printfn. That's the whole list, and honestly? ate. 💅✨

okay that's the whole page, bestie!! this is fend(1), and the changelog above tops out at v0.1.6 (2020-10-05) — that's the version-and-date moment, go off 🫶💖🌸

📦 where this page comes from

nixpkgs unstable: fend 1.5.9
💖 girlified by deepseek-ai/DeepSeek-V4.1-Flash-1017 on 2026-11-04: a language model's rewrite of the original, under its terms