Percentage Calculator
Three percentage tools in one — find a percentage of a number, calculate what percent one number is of another, or solve for the original number.
e.g. 15 for 15%
The number to find the percentage of
Learn More About Percentage Calculator
Three common percentage calculations
Percentage problems usually fall into three groups: finding a percentage of a number, finding what percent one number is of another, and finding the original whole when you know the part and the percentage.
Keeping those patterns separate makes percentage math much easier. This calculator bundles them together so you can switch between the most common use cases quickly.
Example discount and markup math
If a $120 item is discounted by 25%, the savings are $30 and the new price is $90. If that same item later increases by 10%, the new price becomes $99 because the increase is based on the discounted amount, not the original price.
That kind of example shows why percentage changes are easier to understand when you calculate each step directly instead of estimating mentally.
Where reverse percentages are useful
Reverse percentages help when you know a final value and want to work backward. For example, if a sale price of $80 represents 80% of the original price, the original was $100.
This comes up in shopping, tax calculations, grade analysis, finance, and reporting whenever you need to reconstruct the starting value from a known result.
Frequently Asked Questions
How do I find X% of a number?
To find X% of a number, convert the percentage to a decimal (divide by 100) and multiply by the number. For example, 15% of 200 = 0.15 × 200 = 30. This calculator handles the arithmetic for you.
How do I calculate what percent one number is of another?
Divide the smaller number by the larger number and multiply by 100. For example, what percent is 30 of 200? 30 ÷ 200 = 0.15 → 15%. This is useful for understanding discounts, test scores, or proportions.
How do I find the original number if I know the part and the percentage?
Divide the part by the percentage (as a decimal). For example, if 40 is 20% of a number, the original number is 40 ÷ 0.20 = 200. This is called finding the whole from a part.
What are common everyday uses for percentage calculations?
Percentages appear everywhere: calculating discounts at the store, determining tips at restaurants, measuring grade point averages, tracking investment returns, understanding tax rates, and analyzing changes in prices or statistics.