Percentage Calculator
Three of the most common percentage questions, answered instantly. Pick the one that matches what you're solving for — they are NOT the same calculation.
Why three separate calculators?
People searching "percentage calculator" usually mean one of three different math problems, and mixing them up gives you a wrong answer that looks right. "What is X% of Y" finds a portion of a whole (e.g. a 20% tip on $150). "X is what % of Y" finds a ratio between two numbers you already have (e.g. you scored 30 out of 150 — what percent is that?). Percentage change compares an old value to a new one (e.g. your rent went from $1,200 to $1,350 — what's the % increase?). Use the tabs above to pick the right one.
Frequently asked questions
What is the difference between "X% of Y" and "X is what % of Y"?
They're opposite operations. "What is X% of Y" starts with a known percentage and finds a portion of a number (20% of 150 = 30). "X is what % of Y" starts with two known numbers and finds the percentage relationship between them (30 is 20% of 150). Same numbers, different question — use the matching tab above.
How do you calculate percentage increase or decrease?
Subtract the original value from the new value, divide by the original value, then multiply by 100: ((new − original) / original) × 100. A positive result is an increase, a negative result is a decrease.
Is this percentage calculator free and private?
Yes — 100% free, no signup, and every calculation runs locally in your browser with JavaScript. Nothing you type is sent anywhere.
Can I use negative numbers or decimals?
Yes, all three calculators accept decimals and negative numbers and update the result instantly as you type.