Percentage Calculator
Five common percentage calculations, all updating in real time.
1. What is X% of Y?
2. X is what % of Y?
3. % change from X to Y
4. Add X% to Y
5. Remove X% from Y
An all-in-one percentage calculator
This tool bundles the five percentage questions people ask most often into a single screen, with every answer recalculating the instant you type. Instead of remembering whether to multiply, divide, or rearrange a formula, you simply pick the card that matches your question and fill in two numbers. It is built for shoppers comparing discounts, students checking homework, employees working out commissions or raises, and anyone who needs a quick, reliable answer without opening a spreadsheet.
The five cards cover: finding a percentage of a value (What is X% of Y?), expressing one number as a percentage of another (X is what % of Y?), measuring the percentage change between two values, increasing a value by a given percentage, and decreasing a value by a given percentage. Together they handle the vast majority of everyday percentage maths.
How to use it
Choose the card that describes your problem. For example, to find a sale price, use card 5 (Remove X% from Y): enter the discount in the X% box and the original price in the Y box, and the discounted total appears immediately. To check a test score, use card 2 (X is what % of Y?): enter the marks you scored as X and the total available as Y.
Each card shows its result in a highlighted box beneath the inputs, so you can keep several calculations on screen at once and compare them. There is no submit button and nothing to reset between calculations; just edit any field and the matching answer updates on its own.
Tips for accurate results
Remember that percentage change (card 3) is always measured relative to the starting value, so a rise from 50 to 80 is a 60% increase, while the reverse fall from 80 to 50 is a 37.5% decrease. The two figures are not the same, which is a common source of confusion.
Results are rounded to eight significant figures for readability, which is precise enough for prices, grades, tips, and statistics. All maths runs locally in your browser, so the numbers you enter are never uploaded or stored anywhere.