Business

Percentage Calculator

Four everyday percentage questions in one place, with the working shown: a percentage of a number, what percent one number is of another, percentage change, and adding or subtracting a percent.

Calculate

X% of YX is what % of Y% changeAdd or subtract %

Percentage

Fill in both fields to calculate.

Percentage formulas

Question	Formula	Example
What is X% of Y?	X ÷ 100 × Y	20% of 150 = 30
X is what % of Y?	X ÷ Y × 100	30 of 120 = 25%
% change from A to B	(B − A) ÷ A × 100	80 → 100 = +25%
Y plus X%	Y × (1 + X ÷ 100)	1,000 + 18% = 1,180
Y minus X%	Y × (1 − X ÷ 100)	200 − 25% = 150

Why up and down are not symmetrical

A 25% rise from 80 reaches 100, but a 25% fall from 100 only goes back to 75. The base changes, so a fall of 20% is what undoes a 25% rise. The same trap appears in discounts and price rises, and in markup versus margin: see the profit margin calculator.

Common mistakes

Percentage points vs percent
A rate going from 4% to 5% is a rise of 1 percentage point, but a 25% increase.
Adding percentages in sequence
A 10% rise followed by another 10% rise is 21%, not 20%: the second 10% applies to the larger number.
Removing tax by subtracting the rate
To take 18% GST out of a total, divide by 1.18. Use the GST calculator for this.

Frequently asked questions

How do I find a percentage of a number?

Divide the percentage by 100 and multiply by the number. 20% of 150 = 0.2 × 150 = 30.

How do I calculate percentage change?

Subtract the old value from the new one, divide by the old value and multiply by 100. From 80 to 100 is (100 − 80) ÷ 80 × 100 = 25%.

How do I work out what percent X is of Y?

Divide X by Y and multiply by 100. 30 out of 120 is 30 ÷ 120 × 100 = 25%.

Why does a 25% rise and a 25% fall not cancel out?

The base changes. 80 rises 25% to 100, but 100 falls 25% to 75. A 20% fall is what takes 100 back to 80.

Last reviewed 4 October 2026. This tool runs in your browser; nothing you enter is stored or sent to Boostlix.