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Online Percentage Calculator
Percentages show up everywhere: tips, discounts, taxes, grades and raises. This free online percentage calculator handles the three calculations people need most: what is X percent of Y, X is what percent of Y, and the percentage change from X to Y. Pick a mode, enter two numbers, and get an instant answer with the formula shown.
How to use
- Choose the calculation mode that matches your question.
- Enter the X and Y values.
- Click Calculate for an instant answer.
- Read the formula shown under the result to check the math.
The three formulas
What is X% of Y? Multiply Y by X/100. Example: 15% of 80 = 80 x 0.15 = 12.
X is what % of Y? Divide X by Y and multiply by 100. Example: 12 is (12/80) x 100 = 15% of 80.
% change from X to Y: (Y - X) / |X| x 100. Example: from 50 to 75 = (25/50) x 100 = 50% increase.
Everyday uses
A 20% tip on a $45 bill is $45 x 0.20 = $9. A 30% discount on a $120 jacket saves $36. An 8% sales tax on $50 adds $4. A score of 42 out of 50 is 84%.
A raise from $50,000 to $55,000 is a 10% increase. Once you know the three formulas, most everyday percentage questions take seconds.
Frequently asked questions
How do I calculate X percent of Y?
Divide the percentage by 100 and multiply by Y. For example, 15% of 80 is (15 / 100) x 80 = 12. This is the mode to use for tips, discounts, sales tax and commissions.
How do I find what percent X is of Y?
Divide X by Y and multiply by 100. For example, 12 is what percent of 80? (12 / 80) x 100 = 15%. Use this for test scores, completion rates and market share.
How do I calculate percentage change?
Subtract X from Y, divide by the absolute value of X, and multiply by 100. From 50 to 75: (75 - 50) / 50 x 100 = 50% increase. A negative answer means a decrease.
What is the difference between percentage change and percentage difference?
Percentage change is directional: it measures movement from an old value to a new one. Percentage difference compares two values with no order, dividing by their average. Use change for before-and-after questions.
How do I add a percentage to a number?
Multiply the number by (1 + percent/100). To add 15% to 100: 100 x 1.15 = 115. To subtract 20%, multiply by (1 - 20/100), so 100 x 0.80 = 80.
How do I find the original number after a percentage change?
Work backwards. If you paid $1,350 after a 10% discount, that price is 90% of the original, so divide: 1,350 / 0.90 = $1,500. That was the original price.
Why did I get a negative percentage change?
A negative result means the second number is smaller than the first, which is a decrease. For example, from 80 to 60 gives -25%, meaning a 25% decrease.
Can Y be zero when finding X as a percent of Y?
No. Dividing by zero is undefined, so the calculator will ask for a non-zero Y. The same applies to the starting value in a percentage change calculation.