Pick what you want to find, enter two values, and get the answer instantly with the calculation shown step by step.
How to use this calculator
Choose the question you are answering: what is X% of Y, X is what percent of Y, or the change from X to Y.
Enter the two values — the answer appears instantly with the calculation written out.
Switch modes to sanity-check a result from another angle (a discount and its final price should agree).
Use Share to send the exact calculation; the link keeps your numbers.
Formula & method
The three percentage formulas
X% of Y = (X ÷ 100) × Y · X of Y in % = (X ÷ Y) × 100 · Change = ((Y − X) ÷ |X|) × 100
Percentage change is positive for an increase and negative for a decrease. Division by zero is not defined, so Y (or From) must not be 0 in the last two modes.
Example
15% of 200 = (15 ÷ 100) × 200 = 30. And going from 100 to 125 is a +25% change.
Key insights
Percent means 'per hundred': 15% is 15 ÷ 100, or 0.15 as a decimal — multiplying by it takes the percentage directly.
Percentage changes are not symmetric: a 50% loss needs a 100% gain to get back to the start.
Percentage points and percent are different: going from 10% to 12% is +2 points but a +20% relative change.
Sequential discounts do not add up: 20% off then 10% off is 28% off in total, not 30%.
To undo a 25% increase you must decrease by 20%, not 25% — the base has changed.
How to interpret your result
Discounts and tips
'X% of Y' gives the amount saved or added. Subtract it from (or add it to) the price to get the final total.
Scores and rates
'X is what % of Y' turns any fraction into a comparable rate: 42 out of 60 and 21 out of 30 both read 70%.
Growth and drops
Percentage change is measured relative to the starting value. A +25% followed by −25% ends below where it started.
Watch the base
'50% more than 10' (15) and '50% of 10' (5) are different claims. Always ask: percent of what?
Frequently asked questions
How do I calculate a discount?
Use 'What is X% of Y?' with the discount rate and the original price to get the amount saved, then subtract it from the price. A 15% discount on $200 saves $30, so you pay $170.
What is the difference between percentage change and percentage points?
Going from 10% to 12% is a change of 2 percentage points, but a 20% relative increase. This calculator's 'change' mode gives the relative percentage change.
Can percentage change exceed 100%?
Yes. Going from 50 to 150 is a +200% change. Only a decrease is capped: you cannot lose more than 100% of a positive value.
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