Percentage Calculator

What Is a Percentage Calculator?

A percentage represents a fraction of 100. The word comes from Latin "per centum" meaning "by the hundred." When you say 25%, you mean 25 out of every 100. Percentages are used everywhere: tax rates, discounts, interest rates, statistics, grades, and tip calculations. Understanding percentage math is one of the most practical life skills.

How It Works

There are three core percentage operations: Finding a percentage of a number: Multiply the number by the percentage divided by 100. Example: 15% of $200 = $200 × 0.15 = $30. Finding what percentage one number is of another: Divide the part by the whole, multiply by 100. Example: $30 is what % of $200? → ($30 ÷ $200) × 100 = 15%. Percentage change: ((New - Old) ÷ Old) × 100. Example: Price went from $80 to $100 → ((100-80) ÷ 80) × 100 = 25% increase.

Formula Used

Percentage of: X% of Y = (X/100) × Y
What percent: X is what % of Y = (X/Y) × 100
% Change: ((New-Old)/Old) × 100
% Increase: Original × (1 + rate/100)
% Decrease: Original × (1 - rate/100)

Common Percentage Examples

• Shopping: A $75 shirt at 20% off: $75 × 0.80 = $60 (you save $15). Use our discount calculator.
• Tipping: 18% tip on a $65 dinner: $65 × 0.18 = $11.70. Use our tip calculator.
• Tax: 7% sales tax on $500 purchase: $500 × 0.07 = $35 tax. Use our sales tax calculator.
• Salary: 4% raise on $65,000: $65,000 × 1.04 = $67,600.
• Interest: 5% annual on $10,000: $10,000 × 0.05 = $500/year. Use our compound interest calculator.

Quick Percentage Shortcuts

To find 10%: Move the decimal one place left. 10% of $85 = $8.50.
To find 5%: Find 10% then halve it.
To find 15%: Find 10% + 5% (half of 10%).
To find 20%: Find 10% then double it.
To find 25%: Divide by 4.

Related Guides

• Compound Interest Guide