Percentage Calculator
Quick percentage calculations. All processing is local — nothing leaves your browser.
About this tool
The Percentage Calculator handles common percentage computations instantly in your browser. It offers three modes: find a percentage of a number (e.g., what is 15% of 80?), find what percent one number is of another (e.g., 50 is what percent of 200?), and percentage change (e.g., the increase from 100 to 150).
All calculations update in real time as you type — no submit button needed. This is useful for quick mental math checks: calculating tips at a restaurant, figuring out discounts while shopping, computing tax amounts, or analyzing business metrics like revenue growth and margin changes.
Every calculation runs locally in your browser. Your numbers never leave your device.
How to use
- Choose a mode. Select "Find % of a number," "X is what % of Y," or "% Change" from the tab bar at the top of the calculator.
- Enter your values. Type numbers into the input fields. The result updates instantly — no button to click.
- Read the result. The calculated value appears in the result box below the inputs, with a full sentence explanation (e.g., "10% of 200 = 20").
Frequently asked questions
How do I calculate a tip?
Use the "Find % of a number" mode. Enter your tip percentage (e.g., 15 for 15%) and the bill total as the number. For example, "What is 15% of 48?" = $7.20 tip. For a quick estimate, calculate 10% (move the decimal one place) and then add half of that for 15%.
What is percentage change and how is it calculated?
Percentage change measures the relative difference between two values. Formula: ((New - Old) / |Old|) × 100. A positive result means an increase, negative means a decrease. For example, going from 100 to 150 is a +50% change. Use this for tracking revenue growth, weight loss progress, or price changes.
Is my data stored or shared?
No. All calculations happen locally in your browser via JavaScript. The numbers you enter never leave your device and are never stored or transmitted to any server.
Does this work on mobile?
Yes. The Percentage Calculator is fully responsive and works on all modern browsers including iOS Safari and Android Chrome.