What it does
fend is an expression-based calculator with rational arithmetic, complex numbers, variables, number bases and physical units.
fend offers a browser calculator and a terminal interface under the MIT licence. Expressions keep units, support variables and convert with to, as or in; incompatible dimensions are rejected. Temperature conversions distinguish absolute values from differences, including relative treatment in compound units. Output can use exact fractions, recurring decimals, significant figures or decimal places; automatic formatting shows approximate values to ten decimal places. The CLI keeps configurable history and can read piped expressions. Currency conversion separately requires internet exchange-rate retrieval, so local installation does not make every feature offline.
Strengths
- Rational arithmetic and complex numbers
- Supports unit-aware expressions and multiple number bases
Best for
- Checking measurements and calculations in an expression interface
Sources
- GitHub - printfn/fend: Arbitrary-precision unit-aware calculator · GitHub (Oct 26, 2026)
- fend Manual (Oct 26, 2026)
- fend README isolated temperature-example inconsistency (Oct 26, 2026)