Percentage Calculator — All Types
Updated: 2025
Calculate any type of percentage: X% of a number, percentage increase/decrease, percentage difference, and reverse percentage.
How to Calculate Percentages
Percentages express a number as a fraction of 100. The word comes from the Latin "per centum" meaning "per hundred". Percentages are used everywhere in finance: interest rates, tax rates, discounts, investment returns, and inflation.
Common Percentage Formulas
X% of Y: Multiply Y by X/100. Example: 20% of 500 = 500 × 0.20 = 100.
Percentage change: (New − Old) / Old × 100. A positive result is an increase, negative is a decrease.
Reverse percentage: If 80 is 20% of something, the total is 80 ÷ 0.20 = 400.
Percentages in Finance
In finance, percentages appear in: interest rates (AER, APR), tax rates (20%, 40%, 45%), investment returns (% gain/loss), inflation (CPI %), and mortgage rates. Understanding percentage calculations helps you compare financial products accurately.