How to calculate percentages
A percentage is simply a fraction out of 100. This page covers the three questions people ask most often, each with its own mini-calculator above.
What is X% of Y?
Multiply the value by the percentage divided by 100. For example, 15% of 200 is 200 × 0.15 = 30. This is how you work out tips, discounts, and sales tax.
X is what percent of Y?
Divide the first number by the second and multiply by 100. For example, 45 out of 180 is (45 ÷ 180) × 100 = 25%. Useful for scores, shares, and proportions.
Percentage increase or decrease
Subtract the old value from the new value, divide by the old value, and multiply by 100. Going from 120 to 150 is a (30 ÷ 120) × 100 = 25% increase. A negative result means a decrease. This is how you measure growth, markups, and price changes.