Math
Percentage Calculator
Calculate percentages three ways: X% of Y, X is what % of Y, and percentage change between two numbers.
Result
30
20% of 150 = 30
When to use each mode
What is X% of Y? — discounts, tips, taxes, sales commissions.
X is what % of Y? — exam scores, market share, conversion rates.
% change from X to Y — price changes, growth rates, weight loss, stock returns.
Frequently Asked Questions
How do I calculate a percentage of a number?▾
Multiply the percentage (as a decimal) by the number. Example: 20% of 150 = 0.20 × 150 = 30. Use the first mode of this calculator.
How do I calculate percentage change?▾
(New value − Old value) ÷ |Old value| × 100. Example: from 100 to 125 = (125 − 100) / 100 × 100 = +25%. Negative results indicate a decrease. Use the third mode of the calculator.
What's the difference between percentage change and percentage points?▾
Percentage change is relative — going from 5% to 10% is a 100% increase. Percentage points is absolute — going from 5% to 10% is a 5 point increase. News headlines often confuse these. Pay attention.
How do I calculate a tip with percentages?▾
Use mode 1: 20% of $50 = $10 tip. For tip splitting and tax-aware tipping, use our dedicated Tip Calculator.
How do I reverse a percentage (find the original price)?▾
If something is on sale at 20% off and costs $80, divide by (1 − 0.20) = 0.80. So $80 / 0.80 = $100 original price. For percentage markup, divide by (1 + markup_decimal).