Percentage Calculator

Three percentage calculators in one: find X% of a number, what percent one number is of another, and the percentage change between two values.

How to use the Percentage Calculator

Choose the type of question at the top.
Enter the two numbers.
Read the answer and the extra results underneath.

How it works

X% of Y multiplies Y by X and divides by 100. It also shows Y with that percentage added and taken away, which is handy for discounts and price rises.

X is what percent of Y divides X by Y and multiplies by 100.

Percent change divides the difference by the starting value. A change is not symmetrical: going from 80 to 100 is a 25% increase, but going from 100 back to 80 is a 20% decrease, because the starting value is different.

Formula

X% of Y          = X ÷ 100 × Y
X as % of Y      = X ÷ Y × 100
Percent change   = (new − old) ÷ |old| × 100

Example

15% of 240 is 36. 45 is 25% of 180. A price that moves from 80 to 100 has risen by +25%.

Everyday percentage examples

Sales: 25% off $80 is $20 off, so you pay $60.
Sales tax or VAT: adding 8% to $50 gives $54. To remove 20% VAT from a £120 price, divide by 1.20 to get £100.
Pay rise: a raise from $52,000 to $54,600 is a 5% increase.
Test scores: 42 out of 50 is 84%.
Investments: a fall from $1,000 to $850 is a 15% decrease, and you need a 17.6% gain to get back to $1,000.

Quick mental maths

To find 10%, move the decimal point one place left. 5% is half of that, 20% is double it, and 15% is 10% plus 5%. So 15% of $64 is $6.40 + $3.20 = $9.60.

Frequently asked questions

How do I calculate a discount?

Multiply the price by the discount rate. 30% off $70 is 0.30 × 70 = $21 off, so you pay $49.

How do I reverse a percentage increase?

Divide by 1 plus the rate. If a price is $120 after a 20% increase, the original was 120 ÷ 1.20 = $100.

What is the difference between percent change 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.

Why doesn't +25% then −25% get back to the start?

The second change applies to a bigger number. 100 + 25% = 125, and 125 − 25% = 93.75.

Last reviewed October 20, 2026. Spotted an error? Tell us.