How to use the percentage calculator
This page has three calculators. Type into any row and the answer updates instantly.
- X% of Y is useful for tips, commissions, tax and discounts.
- X is what % of Y works for test scores, budget shares and completion rates.
- Percentage change shows price increases, salary raises, growth and drops.
Percentage formulas
X% of Y = Y × X ÷ 100
X as % of Y = X ÷ Y × 100
% change = (New − Old) ÷ Old × 100
Worked examples
- Tip: 18% of a 45.00 bill is 45 × 0.18 = 8.10.
- Exam score: 42 correct out of 50 is 42 ÷ 50 × 100 = 84%.
- Price rise: a product going from 2.50 to 3.00 is a (3 − 2.5) ÷ 2.5 × 100 = 20% increase.
Percent vs. percentage points
If an interest rate goes from 4% to 5%, it rose by 1 percentage point, but by 25 percent (because 1 is 25% of 4). News reports often mix these up, so it helps to know which one is meant.
Frequently asked questions
How do I calculate a percentage of a number?
Multiply the number by the percentage and divide by 100. For example, 15% of 80 is 80 × 15 ÷ 100 = 12.
How do I find what percent one number is of another?
Divide the part by the whole and multiply by 100. For example, 30 out of 120 is 30 ÷ 120 × 100 = 25%.
How do I calculate percentage increase?
Subtract the old value from the new value, divide by the old value and multiply by 100. Going from 50 to 65 is (65 − 50) ÷ 50 × 100 = 30% increase.
Is a 50% increase followed by a 50% decrease the same number?
No. 100 increased by 50% is 150, but 150 decreased by 50% is 75. Percentages always apply to the current value, so they are not symmetric.