2.6k stars · Apache-2.0 or MIT · v1.24.0 (2026-08-23), read from /releases/latest; the repository's own summary page showed the older v1.23.0, so the release page was believed · Track this in Scout
A calculator that understands physical units and refuses sums whose units do not make sense.
▶Repo detailsthe review · specs · pros & cons · install
What it is
A small programming language for scientific calculation, with physical dimensions built into its type system. That means a mistake in units is caught before the sum runs, not after. It ships as a terminal program called numbat, and the same language runs in the browser at numbat.dev. It knows the SI units, imperial units, data sizes, currencies with live rates, and a large library of physical constants.What it is good for. Anyone who does arithmetic where the units matter and a mistake is expensive. Server capacity, transfer times, storage growth, the cost of an API call multiplied out to a month. The problem it removes is the wrong answer that looks right. You ask a question in plain units and get an answer in the units you asked for, and a unit error becomes an error message rather than a number you act on.
- Unit errors are caught, which is the whole point and is genuinely rare in calculators.
- It reads almost like English, so
8 GB / 45 MB/s -> minutesworks as written. - Dual Apache-2.0 and MIT, and there is a full web version if you do not want to install anything.
- It is a calculator, not a spreadsheet. There is nothing to save, share or print.
- Currency rates come from an online source, so that part needs a network connection.
- Learning its small language takes twenty minutes if you want more than one-line sums.
- Qalculate/libqalculate
A much larger desktop calculator that also handles units, symbolic algebra and plotting, with a window rather than a prompt.
Track this in Scout - printfn/fend
The same idea in a smaller package, with arbitrary precision arithmetic and no language to learn.
Track this in Scout - tiffany352/rink-rs
Another unit-aware calculator in Rust, with a large unit database; its README says the repository is moving to Codeberg.
Track this in Scout
# macOS: brew install numbat # With Rust installed: cargo install numbat-cli # Debian or Ubuntu: take the .deb from # https://github.com/sharkdp/numbat/releases/latest # Nothing to install at all: # https://numbat.dev # Then: numbat # and type: 8 GB / 45 MB/s -> minutes
