Three quick tools in one: a percent of a number, what percent one number is of another, and percentage increase or decrease.
A percent of a number: multiply the number by the percent and divide by 100. So 20% of 150 = 150 × 20 ÷ 100 = 30.
What percent one number is of another: divide the first by the second and multiply by 100. So 30 out of 150 = 30 ÷ 150 × 100 = 20%.
Percentage change: subtract the old value from the new, divide by the old value, and multiply by 100. Going from 80 to 100 = (100 − 80) ÷ 80 × 100 = 25% increase. A drop from 100 to 80 is a 20% decrease.
A free tool for quick, everyday percentage math — tips, discounts, grades, and change over time.