Arbitrary-precision unit-aware calculator, mirror of


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fend is an arbitrary-precision unit-aware calculator.

Unique features:

  • Arbitrary-precision arithmetic using rational numbers
  • Full support for complex numbers
  • Binary, octal, hexadecimal and all other bases between 2 and 36
  • Keep track of units, with support for SI, US and UK customary and many historical units
  • Emacs-style CLI shortcuts
  • Trigonometric functions
  • Lambda calculus

See the manual for more information.

Web Interface

fend is now available on the web at


Packaging status

Install fend by running cargo install fend in your terminal. Alternatively you can download the latest stable binaries here.

You can then run fend to start a REPL session:

$ cargo install fend
$ fend
> 1 ft to cm
30.48 cm



You can find the fend manual here.


> 5'10" to cm
177.8 cm
> cos (pi/4) + i * (sin (pi/4))
approx. 0.7071067811 + 0.7071067811i
> 0b1001 + 3
> 0xffff to decimal
> 1 1/2' to cm
45.72 cm
> 1 lightyear to parsecs
approx. 0.3066013937 parsecs
> (x: 2x) pi
approx. 6.2831853071


fend is MIT-licensed. See for more information.

fend optionally includes the GPLv3-licenced definitions.units and currency.units data files from GNU Units. This can be changed via the gpl feature defined in core/Cargo.toml.