Free Online Calculators: 4,400+ Tools

4,400+ free online calculators across 39 categories. Every tool uses sourced figures with a visible last-verified date. Use the category links below to jump to what you need.

United States

See our full United States calculators hub for tax, payroll, retirement, mortgage, savings, debt, and more, all sourced from federal and state government authorities.

Health and wellness

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Options and derivatives

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Aviation flight planning

Meteorology and forecasting

Geospatial and surveying

Cryptography and infosec math

Productivity and time management

More tools live and growing

4,400+ tools live and growing. New tools added regularly. See our United States calculators for the full range of tax, payroll, mortgage, retirement, and financial tools with official government-sourced figures.

How we verify: methodology · editorial standards · reference data.