Free Percentage & Compound Interest Calculators
Four calculators on one page: find what X% of a number is, find what percentage one number is of another, calculate a percentage increase or decrease, and forecast compound interest growth on savings or investments with optional monthly contributions.
For informational purposes only — not financial or investment advice. The compound interest forecast assumes a constant rate and doesn't account for taxes, fees, or market volatility; actual investment results will vary.
Frequently Asked Questions
Is this calculator free to use?
Yes, all four calculators on this page are free with no signup, and results update instantly as you type.
How is compound interest calculated?
Compound interest is calculated by applying your annual rate monthly to the running balance (principal plus any monthly contributions), so interest itself starts earning interest over time.