Percentage Calculator
Calculate percentages four different ways: find a percentage of a number, find what percent one number is of another, find the whole from a part and a percentage, or calculate percentage change.
Recommended Settings
Pro Tips
- •"X% of Y" answers questions like "What is 15% of 200?"
- •"X is what %" answers questions like "30 is what percent of 200?"
- •"X is Y% of?" answers questions like "30 is 15% of what number?"
- •"% Change" answers questions like "What's the percentage increase from 200 to 250?" - a negative result means a decrease
Most Popular
Most users start with "X% of Y" for discounts, tips, and quick percentage math
When to Use This Tool
Calculate a discount amount, sale price, or tip percentage on a bill.
Find what percentage of questions you answered correctly on a test.
Calculate the percentage increase or decrease between two values, like revenue or weight over time.
Work backward from a known part and percentage to find the original whole number.
How It Works
Choose the type of percentage question you're trying to answer from the four tabs
Enter the known values into the input fields
The result updates instantly as you type, using the standard percentage formula for that calculation type
100% Private
Files never leave your device. All processing happens locally in your browser.
Lightning Fast
Powered by Client-side JavaScript arithmetic for optimal performance on modern browsers.
Open Source
Built with verified, open-source libraries. Fully transparent.
Frequently Asked Questions
How do I calculate a percentage of a number?
Multiply the number by the percentage, then divide by 100. For example, 15% of 200 is (15 ÷ 100) × 200 = 30. Use the "X% of Y" tab to calculate this instantly.
How do I find what percent one number is of another?
Divide the part by the whole, then multiply by 100. For example, 30 is (30 ÷ 200) × 100 = 15% of 200. Use the "X is what %" tab for this.
How is percentage change calculated?
Subtract the original value from the new value, divide by the absolute value of the original, then multiply by 100. A positive result is an increase, a negative result is a decrease.
Is my data sent to a server?
No. All calculations happen instantly in your browser using JavaScript. Nothing you enter is transmitted anywhere.
Why can't I divide by zero?
Some calculations, like finding what percent a number is of zero, are mathematically undefined. The result will show as empty when the math doesn't resolve to a real number.