Percentage Calculator
Work out percentages three ways: what is X% of a number, what percent one number is of another, and the percentage increase or decrease between two numbers. It all updates instantly in your browser.
- 🔒 100% private — no uploads
- 🆓 Free, no watermark
- 📱 Works on any device
How to calculate
- 1
Pick a calculation
Choose “% of a number”, “X is what % of Y”, or “% increase / decrease” with the tabs.
- 2
Enter your numbers
Type the two values. The answer updates live as you type — no submit button.
- 3
Read the result
The percentage or amount is shown instantly, all computed on your device.
Why use Percentage Calculator?
Three modes
Percent of a number, a value as a percent of a total, and percentage change between two numbers.
Instant & live
Results update as you type, with no page reloads or waiting.
100% private
Runs entirely in your browser. Nothing you enter is uploaded or stored.
Any device
No install or account — works in any modern browser on desktop or mobile.
Three percentage questions, one tool
Most percentage questions are one of three: “what is 15% of 200?”, “30 is what percent of 200?”, or “what’s the percentage change from 200 to 250?”. This calculator handles all three — tip and discount math, grades, growth rates and markups — and shows the working as you type.
Percentage of vs. percentage change
“What is X% of Y” multiplies; “what percent is X of Y” divides. Change is relative to the old value, which is why a 50% increase followed by a 50% decrease doesn’t return to the start. The tabs keep the three modes separate so you never mix them up.
Practical uses beyond school
Sales tax, tips, commissions, price increases, A/B test lift, body-fat estimates, and success rates all boil down to these three calculations. The live update makes it easy to explore “what if” scenarios: what percent off gets me to my target price, or what increase would double my revenue.
Frequently asked questions
How do I find what percent one number is of another?
Use the “X is what % of Y” tab: enter the part as X and the total as Y. For example, 30 is 15% of 200.
How is percentage increase calculated?
Percentage change = (new − old) ÷ old × 100. Going from 200 to 250 is a +25% increase; 200 to 150 is a −25% decrease.
Do my numbers get uploaded anywhere?
No. Every calculation runs entirely in your browser — your income, loan amount, balances and goals never leave your device. There’s no account and nothing is sent to a server.