Percentage Calculator
Find a percent of a number, reverse it, or measure change. Instant, private, free forever.
How to Calculate Percentages
Every percentage problem is one of three questions. Once you know which one you're asking, the math is simple:
1. What is X% of Y? Convert the percent to a decimal and multiply. Formula: (X / 100) × Y. Example: 15% of 200 = 0.15 × 200 = 30. Use this for discounts, tips, tax, and commissions.
2. X is what percent of Y? Divide the part by the whole, then multiply by 100. Formula: (X / Y) × 100. Example: 30 is what percent of 150? (30 / 150) × 100 = 20%. Use this for test scores, completion rates, and market share.
3. What is the percent change? Subtract the old value from the new value, divide by the old value, multiply by 100. Formula: ((New − Old) / Old) × 100. A positive answer is an increase, negative is a decrease. Example: 80 to 100 = ((100 − 80) / 80) × 100 = 25% increase.
Where Percentages Show Up Every Day
Percentages quietly run most money decisions. A 20% tip on a $85 bill is $17. A 30% off sale on a $150 jacket saves $45. A 7.5% sales tax on $240 adds $18. Investment returns, loan interest, salary raises, grade curves, and battery levels are all percentages in disguise. Getting fluent with the three formulas above means never second-guessing a deal, a bill, or a paycheck again.
One common trap: percentage points vs. percent. If an interest rate moves from 4% to 6%, that's a 2 percentage point rise, but a 50% percent increase. Politicians and marketers mix these up on purpose. Now you won't.
Frequently Asked Questions
How do you calculate a percentage?
Divide the part by the whole and multiply by 100. Example: to find what percent 30 is of 150, compute (30 / 150) × 100 = 20%.
How do I calculate percent increase or decrease?
Subtract the original value from the new value, divide by the original value, and multiply by 100. Positive means increase, negative means decrease. From 80 to 100 is a 25% increase.
What is X percent of Y?
Convert the percent to a decimal (divide by 100) and multiply by Y. 15% of 200 = 0.15 × 200 = 30.
How do I convert a percentage to a decimal?
Divide by 100, or move the decimal point two places left. 45% becomes 0.45.
Is this percentage calculator free?
Yes, 100% free with no signup. All calculations happen instantly in your browser.
Does the calculator store my numbers?
No. Everything is computed locally in your browser. Your numbers are never sent to any server.