How to use the Percentage Calculator
- Choose the question type that matches what you are asking.
- Enter the two known values in the fields shown.
- Read the answer along with the arithmetic used to reach it.
- For change calculations, check which value you entered as the starting point — the answer depends on it.
How the calculation works
A percentage is a fraction with a denominator of 100, so every percentage problem reduces to a ratio. Finding 15% of a number multiplies it by 0.15. Expressing 36 as a percentage of 240 divides and multiplies by 100. Percentage change divides the difference by the original value, which makes the choice of original value part of the answer rather than a detail.
That base-dependence causes two effects worth remembering. Increases and decreases of equal percentage do not cancel — a 25% rise followed by a 25% fall leaves you 6.25% below where you started. And successive percentages multiply: two 10% discounts give 19% off, not 20%, because the second applies to the already-reduced figure.
Of: x = p/100 × n | Is-what-percent: p = a/b × 100 | Change: p = (new − old)/old × 100Source: Elementary proportional arithmetic; percentage change convention as used in official statistics reporting.
Worked example
A subscription rises from 34.50 to 41.99 and you want the percentage increase.
- Difference = 41.99 − 34.50 = 7.49.
- Divide by the original: 7.49 / 34.50 = 0.21710.
- Multiply by 100.
A 21.71% increase. Reversing it would require a 17.84% cut, because the base is now larger.
Frequently asked questions
What is the difference between percentage points and percent?+
A rate moving from 4% to 6% has risen 2 percentage points but 50 percent. Statistics reporting uses percentage points precisely to avoid that ambiguity.
How do I reverse a percentage increase?+
Divide rather than subtract. To strip a 20% markup from 96, divide by 1.20 to get 80 — subtracting 20% of 96 would incorrectly give 76.80.
Why do two 10% discounts not equal 20% off?+
The second discount applies to the reduced price. 100 becomes 90, then 81, which is 19% off rather than 20%.
How do I calculate the original price before a discount?+
Divide the sale price by one minus the discount as a decimal. A 30%-off item costing 63 was originally 63 / 0.70 = 90.
Last reviewed August 31, 2026. We review this page whenever the underlying formula, tax year, published rate or standard changes.