Free online calculator for everyday and advanced math

Calcul.io is a multi-line calculator that keeps the expression and result together. Enter ordinary arithmetic, percentages, formulas, variables, unit conversions, dates, currencies, or supported math functions. Each line is editable, so you can change an earlier value and immediately see how the rest of the calculation responds.

Calculate in the way you write

Start with an expression such as 18% of 245, 5 km to miles, or today + 30 days. For longer work, give a value a name and reuse it on later lines. Calcul.io is useful for quick checks as well as calculations you want to inspect, adjust, and share.

Explore the worked examples, read the calculator instructions, or browse the complete math function reference and constants reference. No account is required.