About Calculator Tools
Calculator Tools is a free collection of 1,457 calculators across 200 categories, covering maths, finance, health, science, engineering, construction, conversions and everyday questions.
How the calculators work
Every calculation runs in your browser. Nothing you type is sent to a server, so results appear as you type and your numbers stay on your device. Each calculator page shows the formula it uses, a worked example and — where it helps — a step-by-step breakdown, so you can check the answer rather than take it on trust.
Where the numbers come from
Unit conversions use exact internationally agreed definitions where one exists — an inch is 25.4 mm, a pound is 0.45359237 kg. Scientific constants follow standard published values. Where a calculator relies on a typical figure rather than a fixed constant (a material density, an average energy intake, a tax band), the figure is shown as an input you can change, so the result reflects your situation rather than an assumption.
What this site is not
Results are informational estimates. Finance calculators do not account for every fee, tax or rule that may apply to you, and health calculators are not a medical assessment. See the disclaimer for details.
Found a mistake?
Corrections are genuinely welcome — if a formula or a default value looks wrong, please get in touch.