How to use it
Pick the question that matches yours and type the two numbers. The answer shows right away, with no button to press. All three questions use the same idea, turned around.
The formulas
| Question | Formula | Example |
|---|---|---|
| What is X% of Y? | Y × X ÷ 100 | 20% of 1,500 = 1,500 × 20 ÷ 100 = 300 |
| X is what % of Y? | X ÷ Y × 100 | 45 of 60 = 45 ÷ 60 × 100 = 75% |
| X is Y% of what? | X ÷ (Y ÷ 100) | 30 is 12% of 30 ÷ 0.12 = 250 |
"Percent" means "out of a hundred". So 20% is 20 out of every 100, or 0.20 as a decimal. To turn any percent into a decimal, divide it by 100.
Worked example
A ₱1,500 bill with a 12% service charge: 1,500 × 12 ÷ 100 = ₱180. The total is ₱1,680.
Common questions
How do I work out a percentage in my head?
Find 10% first by moving the decimal point one place left. 10% of 850 is 85. Then build from it: 5% is half of that (42.5), 20% is double (170), and 15% is 10% plus 5% (127.5).
Is X% of Y the same as Y% of X?
Yes. 8% of 50 and 50% of 8 are both 4, because both are 8 × 50 ÷ 100. Pick whichever is easier to do in your head.
How do I find a percentage increase or decrease?
That is a different question. It compares an old number with a new one. Use the percentage change calculator for that.
Last checked: 2026-09-25