Percentage Calculator
Answer the three everyday percentage questions in one place, with the formula shown for each result.
Result
Enter your values and select Calculate to see the result.
How to use this calculator
- Choose the question you want to answer from the first menu.
- Fill in the two boxes that appear. The result updates as you type.
- Negative numbers and decimals are allowed.
Formula
- P% of a number:
result = number × P ÷ 100 - X is what percent of Y:
percent = X ÷ Y × 100 - X is P% of what total:
total = X ÷ (P ÷ 100)
A percentage is simply a fraction of 100, so 25% means 25 ÷ 100 = 0.25.
Worked example
15% of 240
240 × 15 ÷ 100 = 36.
45 out of 180 as a percentage
45 ÷ 180 × 100 = 25%.
30 is 12% of what?
30 ÷ 0.12 = 250.
Assumptions and limitations
- When finding what percent X is of Y, Y cannot be zero because division by zero is undefined.
- When solving for a total, the percentage cannot be zero.
- Results show up to eight decimal places.
Frequently asked questions
How do I calculate a percentage of a number in my head?
Find 10% by moving the decimal point one place left, then scale. For example, 10% of 240 is 24, so 15% is 24 + 12 = 36.
Is “X% of Y” the same as “Y% of X”?
Yes. Multiplication is commutative, so 8% of 50 and 50% of 8 are both 4. This can make some mental calculations easier.
How do I calculate a percentage increase?
Use the Percentage Change calculator, which compares an original and a new value.