Percentage Calculator
Find P% of a number, what percent one number is of another, or the whole from a part and its percentage, with the answer written out in words.
Most everyday percentage questions come in three forms: finding a percentage of a number (15% of 240), finding what percentage one number is of another (240 out of 800), or working back to the whole when you only know a part and its percentage. Pick the question, enter the numbers you have, and the answer is shown with the sentence written out so you can check it reads the way you meant.
How to use this tool
- Choose the question you want answered.
- Enter the percentage P and the values X and Y that question uses — the note under each box says which questions need it.
- Read the answer and the sentence version below it.
- For "What is P% of X?", also see X increased and decreased by that percentage.
Formula
P% of X = P ÷ 100 × X
X as a percent of Y = X ÷ Y × 100
Whole = X ÷ (P ÷ 100)
"Percent" means per hundred, so every percentage is a fraction with 100 underneath. All three formulas are the same relationship — part = percentage × whole — rearranged for whichever value is unknown.
Example
A $240 jacket is 15% off. 15% of 240 = 0.15 × 240 = 36, so you save $36 and pay $204 (the "X − P%" figure). If you scored 240 points out of 800, 240 ÷ 800 × 100 = 30%. If $240 was a 15% deposit, the full price is 240 ÷ 0.15 = $1,600.
Frequently asked questions
How do I work out a percentage in my head?
Find 10% by moving the decimal point one place left, then scale it. 10% of 240 is 24, 5% is half of that (12), so 15% is 24 + 12 = 36.
Is X% of Y the same as Y% of X?
Yes. Multiplication works in either order, so 8% of 50 and 50% of 8 are both 4. Use whichever is easier to work out.
How do I add a percentage to a number?
Multiply by 1 plus the percentage as a decimal: 240 + 15% = 240 × 1.15 = 276. To take it off, multiply by 1 minus it: 240 × 0.85 = 204.
Why doesn’t adding 20% and then removing 20% get me back to the start?
The second percentage is taken of a larger number. 100 + 20% = 120, but 120 − 20% = 96. To undo a 20% increase, divide by 1.2 instead.
What is the difference between percent and percentage points?
Percentage points measure the gap between two percentages. A rate moving from 4% to 5% is a rise of 1 percentage point, but a 25% increase relative to the old rate.
Last updated: 2026-10-30