Percentage Calculator
“Percent” means “per hundred”, so every percentage question is really a question about a fraction with 100 on the bottom. Pick the question you have — the three modes cover almost every percentage problem on a worksheet — and the calculator shows each step so you can copy the method, not just the answer.
Answer
15% of 80 = 12
Step by step
- Change the percent to a decimal by dividing by 100: 15% = 0.15.
- Multiply by the number: 0.15 × 80 = 12.
Answer: 12
Still stuck? Ask the tutor about these steps
How it works
(X ÷ 100) × Y(X ÷ Y) × 100X ÷ (P ÷ 100)All three questions use one relationship: part = percent × whole, with the percent written as a decimal. Knowing any two of the three pieces lets you find the third.
To turn a percent into a decimal, divide by 100 (move the decimal point two places left): 15% = 0.15, 7.5% = 0.075, 120% = 1.2. To go back, multiply by 100.
A quick mental check: 10% of a number is the number with the decimal point moved one place left, and 1% is two places. 15% of 80 is 10% (8) plus 5% (4) = 12.
Want to see why it works? How to calculate a percentage — with an interactive hundred grid.
Worked example
A test has 40 questions and you got 34 right. What percentage is that?
- 34 ÷ 40 = 0.85
- 0.85 × 100 = 85%
- You scored 85%.
Frequently asked questions
How do I calculate a percentage of a number?
Divide the percent by 100 and multiply by the number. For 20% of 150: 20 ÷ 100 = 0.2, and 0.2 × 150 = 30.
How do I find what percent one number is of another?
Divide the part by the whole and multiply by 100. 18 out of 24 is 18 ÷ 24 = 0.75, so 75%.
Is X% of Y the same as Y% of X?
Yes. Multiplication can be done in any order, so 8% of 50 equals 50% of 8 — both are 4. This trick makes some problems easy to do in your head.
Can a percentage be more than 100?
Yes. 100% is the whole amount, so 150% of 40 is one and a half times 40, which is 60. Percentages above 100 are common when describing growth.