Who runs it
I built Kalkuli because most online calculators either give you a bare number with no explanation, or hide the useful part behind pop-ups. When I check a calculation I want to see the steps, know which formula was used, and be told when a problem has two answers rather than silently getting one. That's the standard every tool on this site is held to.
What's here
- Six calculators: a scientific calculator that takes whole expressions, and solvers for quadratics, triangles, statistics, units and matrices. Each one shows its working.
- Guides in the Learn section that explain the maths with worked examples you can check in the calculators, such as why sin(30) sometimes gives −0.988 or when a triangle has two answers.
- Reference pages: a formula sheet and the physical constants the calculators use.
How the calculators are checked
The maths behind every tool is separated from the page layout so it can be tested on its own. Before any change goes live it has to pass an automated test suite (currently 128 checks) covering things like:
- order of operations, implicit multiplication and bracket handling;
- exact trig values at standard angles, and errors for undefined cases such as tan 90°;
- both solutions of the ambiguous SSA triangle case, and rejection of impossible triangles;
- sample and population statistics against hand-worked values;
- 3×3 inverses, by checking that A × A⁻¹ comes back as the identity matrix;
- every worked example published in the guides.
Physical constants are the CODATA 2022 recommended values. Unit conversion factors use the legal definitions (for example 1 inch = 25.4 mm exactly, and 1 UK gallon = 4.54609 litres exactly).
Found a mistake?
Please tell me. Include what you typed and what you expected, and I'll check it. If it's a genuine error I'll fix it, add a test so it can't come back, and note it in the change log below.
Privacy and advertising
Every calculation runs in your browser. Nothing you type into a calculator is sent to a server. Kalkuli is free to use and is supported by advertising from Google AdSense. The privacy policy explains what cookies are used and how to control them.
Change log
- : New expression engine for the scientific calculator (whole expressions, implicit multiplication, exact trig values, clearer error messages). Triangle solver now finds both answers in the ambiguous case. Matrix calculator handles 3×3. Unit converter gains area, volume, speed and power. New Learn section with eight guides.
- : First version of Kalkuli published.