Free Percentage Calculator
Solve the three percentage problems you meet every day: what percent X is of Y, what X percent of Y equals, and the percent increase or decrease between two numbers.
This free percentage calculator solves the three classic percentage problems: what percent X is of Y, what X percent of Y is, and the percent increase or decrease between two numbers. It runs entirely in your browser with no signup.
Tips, discounts, sales tax, grades, and pay raises are all one of these three problems. See Terms of Use.
The three percentage problems, explained
Almost every percentage question you will ever meet is one of three problems. Once you recognize which one you are solving, the formula is simple, and you never have to guess again.
Problem one: X is what percent of Y? Divide X by Y and multiply by 100. If you scored 42 points out of 50 on a test, 42 divided by 50 is 0.84, times 100 gives 84 percent. This is the formula behind grades, tips judged against the bill, and sale prices compared to the original.
Problem two: What is X percent of Y? Convert the percent to a decimal by dividing by 100, then multiply by Y. A 15 percent tip on a 60 dollar bill is 0.15 times 60, which equals 9 dollars. This is the formula behind sales tax, commissions, interest charges, and growth targets.
Problem three: What is the percent change between two numbers? Subtract the old number from the new number, divide by the old number, and multiply by 100. If your electric bill went from 120 to 150 dollars, 30 divided by 120 is 0.25, a 25 percent increase. If it fell to 90 dollars, the same math gives a 25 percent decrease. This is the formula behind price hikes, pay raises, and population change.
The most common mistake is dividing by the wrong base. A 50 percent increase followed by a 50 percent decrease does not return you to the start: raising 100 by 50 percent gives 150, but lowering 150 by 50 percent removes 75, leaving 75. The decrease applies to the larger number, so it bites harder. Always ask: percent of what? That question keeps every percentage calculation honest.
Percentage calculator questions
What is X percent of Y?
Convert the percent to a decimal by dividing it by 100, then multiply by Y. For example, 15 percent of 60 is 0.15 times 60, which equals 9. The second tab of this calculator does this math for you.
How do you calculate what percent one number is of another?
Divide the first number by the second number, then multiply by 100. If you scored 42 out of 50 on a test, 42 divided by 50 is 0.84, times 100 gives 84 percent. The first tab of this calculator solves it instantly.
How do you find the percent increase or decrease between two numbers?
Subtract the old number from the new number, divide the result by the old number, and multiply by 100. A bill rising from 120 to 150 is a 25 percent increase. A positive result means an increase, a negative result means a decrease.
Why does a 50 percent increase followed by a 50 percent decrease not return to the original number?
Because the two percentages use different bases. Raising 100 by 50 percent gives 150, but lowering 150 by 50 percent removes 75, leaving 75. The decrease applies to the larger number, so it is bigger in absolute terms.