ToolFigure is a free library of online calculators and tools, built and maintained by Shahid Imran. It exists for one reason: most calculator websites give you a number and ask you to trust it. ToolFigure shows you the number and the maths behind it.
How every tool page works
Each page follows the same rules: the tool itself first, then the formula written out in plain language, a worked example with real numbers you can verify with a pencil, a plain statement of what the result does not cover, and answers to the questions people actually ask about that calculation.
Accuracy & testing
Every calculator is tested against hand-worked examples before it is published, and pages carry a last-updated date. If you spot a result that looks wrong, please tell us — corrections are published, not hidden.
Privacy by design
All calculations run in your own browser. The numbers you enter are never sent to a server, which means there is nothing for us to store, sell or lose.
What ToolFigure is not
It is not a lender, a doctor or a financial adviser. Finance and health pages give educational estimates with disclaimers; important decisions deserve a qualified professional and official documents.