Percentage Calculator
Every percentage problem in one place — live results as you type, spreadsheet-style decimal control, and exact arithmetic that never shows floating-point garbage. Free, instant, no sign-up.
Enter your values to see instant results:
Keyboard shortcuts
| Tab / Shift+Tab | Next / previous field |
| ↑ / ↓ | Step a value by 1 (Shift: 10, Alt: 0.1) |
| Enter | Copy the focused row's result |
| [ / ] | Fewer / more decimal places |
| Esc | Clear the field |
How to calculate percentages
A percentage is just a fraction with 100 as the denominator — per centum, "per hundred." Every percentage question you'll meet in real life reduces to one of three basic problems, and each has its own row above:
- Find a percentage of a number. Multiply, then divide by 100: 15% of 200 is 200 × 15 ÷ 100 = 30. This is the tip-and-tax problem.
- Express one number as a percentage of another. Divide the part by the whole, times 100: 30 is 30 ÷ 150 × 100 = 20% of 150. This is the test-score problem.
- Find the change between two numbers. Subtract, divide by the starting value, times 100: going from 50 to 75 is a +50% change. This is the price-went-up problem — measured against where you started, which is why a +50% rise followed by a −50% fall doesn't get you back where you began.
The remaining rows are the everyday variations: applying an increase or a decrease to a number, the symmetric percentage difference between two values, and working backwards to the original number when you only know a part and its percentage. Shopping? The percent off calculator speaks in prices and savings directly.
Small habits that prevent most percentage mistakes: anchor on 10% and scale it; remember that a% of b always equals b% of a (8% of 50 = 50% of 8 = 4); and never add sequential percentages — a 20% discount followed by 30% off is 44% off, not 50%. That last one costs shoppers real money, and the research on it is worth two minutes of your time.
Percentage FAQ
How do I calculate a percentage of a number?
Multiply the number by the percentage, then divide by 100. So 15% of 200 is 200 × 15 ÷ 100 = 30. A handy mental shortcut: 10% is the number with the decimal point moved one place (10% of 200 = 20), and you can build most percentages from that — 15% is 10% plus half of it.
How do I work out what percent one number is of another?
Divide the part by the whole and multiply by 100: part ÷ whole × 100. If 30 out of 150 students passed, that's 30 ÷ 150 × 100 = 20%. The order matters — the number after "of" is always the divisor.
What is the percentage change formula?
Percentage change = (new − old) ÷ old × 100. Going from 50 to 75 is (75 − 50) ÷ 50 × 100 = +50%; going from 75 back to 50 is −33.33%, not −50% — the change is always measured against the starting value. The percentage change calculator handles both directions.
What is the difference between percentage change and percentage difference?
Percentage change is directional: it measures movement from an old value to a new one, relative to the old value. Percentage difference compares two values with no direction, relative to their average — useful when neither number is the "starting" one, like comparing two prices. The full breakdown is in change vs. difference vs. points.
How does this calculator round results?
Exact answers are shown exactly (0.495 stays 0.495). Repeating decimals are rounded half away from zero at your chosen precision — the .0← and .00→ buttons work like a spreadsheet, and results are recomputed from the exact value, so no rounding error ever accumulates. Details on the methodology page.
Is anything I type sent anywhere?
No. The calculator runs entirely in your browser; your numbers never leave your device, and it keeps working once the page has loaded even if your connection drops. There are no accounts and nothing to install.
Articles
all →Changelog
all →- 2.0.1 — Launch-feedback polish 2026-08-31
- 2.0.0 — Complete rebuild 2026-08-30