Percentage Calculator

The Percentage Calculator solves the three percentage problems people actually need, in one compact tool: (1) What is X% of Y? (2) X is what percent of Y? (3) What is the percentage change (increase or decrease) from X to Y? Each mode updates live as you type, with clear labels so you always know what you are computing.

Percentages are everywhere — discounts, taxes, tips, interest rates, exam scores, growth metrics, survey results — yet mental percentage math is error-prone, especially for non-round numbers. This tool removes the arithmetic friction so you can focus on what the number means. Computing 17.5% of 8,400 by hand is slow and risky; this calculator gives the answer (1,470) instantly.

Mode 1 (X% of Y) answers questions like 'What is 15% of 200?' (answer: 30) — useful for tips, discounts and tax. Mode 2 (X is what % of Y) answers '30 is what percent of 200?' (answer: 15%) — useful for exam scores, survey results and ratios. Mode 3 (percentage change) answers 'What is the percent increase from 200 to 250?' (answer: 25%) — useful for growth metrics, price changes and comparisons.

The percentage-change mode correctly handles both increases and decreases, labeling the result accordingly, and guards against division by zero. Everything runs locally in your browser.