Percentage Of
Find a percentage of a number, or work out what percent one number is of another, with worked examples for tips, discounts and test scores.
Results
Result
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Educational estimates · not financial advice · free, no signup
Formula / how it works
X% of Y = X ÷ 100 × Y. X is what % of Y = X ÷ Y × 100.
Read the guide: Percentage Change vs Percentage Points
Detailed guide
What it is, how to use it, how to read the numbers, common mistakes, a worked example, formulas, and FAQs.
What this calculator is
Percentages answer two common questions: what is 20% of 150, and what percentage is 30 out of 150? This calculator handles both. In the first mode you give a percentage and a base and get the amount. In the second you give two numbers and get the percentage one is of the other. Everyday uses are endless: tips, sales tax, discounts, exam marks, commission and budget shares. The calculation is simple, but it is easy to slip on which number is the base. The base is always the number the percentage is measured against, the whole.
When to use / who it helps
- You need a percentage of a price, such as a tip or tax.
- You want to know what percentage a score or part is of a total.
- You are checking a discount amount.
- You are working out a share of a budget.
- You are checking a homework answer.
How to use
Steps
- Choose the mode: What is X% of Y, or X is what % of Y.
- Enter X and Y according to the mode.
- In the first mode, X is the percentage and Y is the base.
- In the second mode, X is the part and Y is the whole.
- Read the result.
- Check by reversing the calculation.
How to interpret results
- In the first mode the result is an amount in the same units as Y.
- In the second mode the result is a percentage.
- A percentage above 100 means the part is larger than the whole.
- The base is always the number after "of".
- For percentage change, use the percentage change calculator.
Common mistakes & gotchas
- Swapping the part and the whole.
- Entering the percentage as a decimal, such as 0.2.
- Using the new value as the base for a change.
- Confusing percentage points with percent.
- Rounding before multiplying.
Worked example
Worked example — 20% of 150, and 30 out of 150
- Mode 1: 20 ÷ 100 × 150 = 0.2 × 150 = 30.
- Mode 2: 30 ÷ 150 × 100 = 20%.
- A 15% tip on a $48 meal: 0.15 × 48 = $7.20.
- Check: 7.20 ÷ 48 × 100 = 15%.
Result: 20% of 150 is 30, and 30 is 20% of 150.
To load the form's own demo values, tap Try example above the Calculate button.
How to calculate / formula
X% of Y = X ÷ 100 × Y. X is what % of Y = X ÷ Y × 100.
Frequently asked questions
How do I calculate a percentage of a number?
Divide the percentage by 100 and multiply by the number.
How do I find what percent one number is of another?
Divide the part by the whole and multiply by 100.
What is 10% of a number?
Move the decimal point one place to the left.
How do I calculate a discount?
Multiply the price by the discount percentage to get the amount off, then subtract.
Can a percentage be more than 100?
Yes, when the part exceeds the whole.
What is the difference from percentage change?
Percentage change compares two values over time; this tool compares a part with a whole.