Free Percentage Calculator
Free Percentage Calculator is a free online tool by US AI. Calculate X% of Y, find what percent X is of Y, or solve a reverse percentage — instantly, right here. It runs completely in your browser — no signup, no download, works on mobile and desktop.
🧮 Calculate now
📖 How to use
- Pick a mode above: "What is X% of Y?", "X is what % of Y?", or "X is Y% of what?".
- Enter your two numbers and press Calculate — the answer and the formula appear instantly.
- Your work stays on your device; nothing is uploaded anywhere.
✨ Why use this tool?
Percentages are everywhere — discounts at the store, tips at a restaurant, tax on a bill, and marks on an exam. A percentage is simply a part of a whole, written out of 100: 25% means 25 out of every 100. US AI's free percentage calculator handles the three calculations people use most: X% of Y (like 15% of 200), what percent X is of Y (like what percent of 200 is 30), and reverse percentage (like 30 is 15% of what). Everything is computed instantly on your device — fast, private and 100% free forever. Bookmark this page and share it with anyone who needs it.
❓ Frequently asked questions
What is the difference between a percentage and percentage points?
Going from 20% to 25% is a 5 percentage-point rise, but a 25% relative increase. Percentage points measure the raw gap; percent change measures growth relative to the starting value.
How do I calculate reverse percentage?
If 30 is 15% of a number, divide: 30 / 0.15 = 200. The third mode of our calculator does this instantly — just enter 30 and 15.
Is there an easy mental trick for percentages?
Use the 10% rule: to find 10% of any number, move the decimal point one place left (10% of 250 = 25). Build from there — 20% is double, 5% is half of 10%, and 15% is 10% + 5%.
Can a percentage be more than 100%?
Yes. 100% of something equals the whole; 150% means one and a half times the whole. Growth figures often exceed 100% — a 200% increase means the value tripled.
What does a negative percentage mean?
A negative percentage means a drop below zero, like a −10% return on an investment, or a value that fell relative to its starting point.