Percentage Calculator
Work out what X% of Y is, what percent X is of Y, and the percentage change between two numbers — instantly, entirely inside your browser.
What is a Percentage Calculator?
A percentage calculator handles the three most common percent problems people run into: finding what a percentage of a number is, figuring out what percentage one number is of another, and measuring how much a value increased or decreased in percentage terms. Each of these looks simple, but they use different formulas, and it's easy to reach for the wrong one under time pressure — this tool separates them into three clearly labeled calculators so there's no guessing about which one to use.
It's built for anyone who needs a quick, accurate percentage without doing the arithmetic by hand: shoppers checking a discount, students working through a percentage word problem, professionals comparing sales figures or budget changes year over year, or anyone splitting a bill, tip, or commission.
GuideHow to use it
How each calculation works
What is X% of Y? multiplies Y by X divided by 100 — for example, 20% of 150 is (20 ÷ 100) × 150 = 30. X is what percent of Y? divides X by Y and multiplies by 100, so 30 out of 150 is (30 ÷ 150) × 100 = 20%. Percentage change from X to Y subtracts X from Y, divides by the absolute value of X, and multiplies by 100 — going from 150 to 180 is ((180 − 150) ÷ 150) × 100 = a 20% increase, while going from 150 to 120 is a 20% decrease. The sign of the result shows the direction: positive means an increase, negative means a decrease.
Why it helpsFeatures & benefits
Common uses for percentage calculations
Percentages show up constantly in everyday and professional life: working out a discount at checkout, calculating a tip, comparing test scores, tracking how much a stock or budget line moved between two periods, or converting a fraction of a dataset into a shareable statistic. Because each of these situations calls for a different one of the three formulas above, having them side by side removes the guesswork of remembering which one applies.
Why this runs entirely in your browser
The numbers entered here are processed with plain JavaScript running locally in the tab. Nothing is uploaded, logged, or sent to a server, so it keeps working offline once the page has loaded and nothing typed into it persists after the tab closes.
Getting an accurate result
Double-check which number goes in which field — swapping X and Y in the "percentage change" calculator flips an increase into a decrease and vice versa. For the "what percent of" calculator, Y should be the whole or total amount and X the part being measured against it. If a result looks unexpected, it's almost always worth re-checking which value was entered as X and which as Y.
Frequently asked questions
A few things people usually want to know before trusting the numbers.
Multiply Y by X and divide by 100. For example, 15% of 200 is (15 ÷ 100) × 200 = 30. The first calculator on this page does this automatically as you type.
Divide the part by the whole and multiply by 100. For example, 45 out of 60 is (45 ÷ 60) × 100 = 75%. Use the second calculator for this.
Subtract the starting value from the new value, divide by the starting value, and multiply by 100. A positive result is a percentage increase; a negative result is a percentage decrease.
Yes. All three calculators accept negative numbers and decimals, and the results update live as you type.
No. All calculations run locally in your browser. Nothing entered here is sent to a server, stored, or shared.