Mobile-first
Calculators should be fast and usable when someone is standing in a store, on a job site, at dinner, or answering a question from their phone.
About All The Calculations
All The Calculations is a growing library of fast, mobile-friendly tools for the numbers people need in real life: unit conversions, paychecks, payments, project estimates, and everyday decisions.
Who built this
The site is built by Austin Witherow, who maintains every calculator page and its sources. Austin runs BuildLeanSaaS.com, which builds small, practical software products and web tools. Found a mistake? Use the contact page and it will be fixed.
Most calculators online return a number and stop there. That is fine until the number matters: when you are about to pay a bill, order materials, or send an estimate to someone else. Then you need to know which formula was used, what was assumed, and where the answer stops being reliable.
So every calculator here puts a quick answer first, followed by the formula, worked examples, assumptions, and caveats you need to trust or check the answer later.
Transparent formulas
Pages show the formula, assumptions, examples, and limitations instead of only returning a number.
Easy to audit
Anyone reading the page later, whether a teammate, a client, or you next month, should be able to see what was calculated and why.
How the library grows
New calculators are added a few at a time. Each one has to work with realistic inputs, show its formula, include an example you can check by hand, and be honest about its limitations before it is published.
Read the methodology for how calculator pages are written and checked, or suggest a calculator.