Percentage Calculator
How to Calculate a Percentage
A percentage is just a number out of 100. Once you know the basic formula it's quick to work out by hand, and the calculator below does it instantly.
Calculate a percentage
What is X% of a number?
Result
30
X is what percent of Y?
Result
20%
Percentage increase / decrease
Change
+25%
Percent off (discount)
Final price
60
You save
20
Add or subtract a percentage
Result
220
The basic formulas
- Percent of a number: (percent ÷ 100) × number. e.g. 20% of 80 = 0.2 × 80 = 16.
- One number as a percent of another: (part ÷ whole) × 100. e.g. 16 out of 80 = 20%.
- Percentage change: ((new − old) ÷ old) × 100.
A worked example
Say a $50 item is 30% off. The discount is (30 ÷ 100) × 50 = $15, so you pay $35.
To check what percentage $15 is of $50: (15 ÷ 50) × 100 = 30%. The two formulas are mirror images of each other.
Frequently asked questions
How do I find a percentage of a number?
Divide the percentage by 100 and multiply by the number. For 20% of 80: 0.2 × 80 = 16.
How do I work out what percentage one number is of another?
Divide the part by the whole and multiply by 100. For 16 out of 80: (16 ÷ 80) × 100 = 20%.
Can the calculator do this for me?
Yes — the calculator above handles all the common percentage questions instantly.
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