Percentage Calculator
Free percentage calculator with three modes - find X% of Y, what percent X is of Y, or reverse percentage calculations.
About Percentage Calculator
This free percentage calculator handles every common percentage computation you might need. It has three built-in modes that cover the most common scenarios.
Three Calculation Modes
The first mode answers the classic question: what is X% of Y? Enter a percentage and a base number to instantly see the result. This is useful for calculating tips, taxes, commissions, and markups.
The second mode solves the inverse: X is what percent of Y? Enter two numbers and the calculator determines the percentage relationship between them. This is helpful for grading, statistics, and comparing values.
The third mode performs reverse percentage calculations. If you know the final value after a percentage increase or decrease, this mode finds the original value. For example, if a sale price is $72 after a 10% discount, the original price was $80.
How Percentages Work
A percentage is simply a fraction expressed out of 100. The word itself comes from the Latin per centum, meaning "by the hundred." Percentages make it easy to compare proportions, express ratios, and communicate changes in value across different contexts.
Common Uses
- Shopping discounts and sale price calculations
- Tax and tip computations at restaurants
- Grade and score conversions in education
- Financial analysis such as profit margins and interest rates
- Data analysis and statistical reporting
Looking for a specific use case? The discount calculator handles sale price math, and the Profit Margin Calculator applies percentage math to business pricing. All calculations happen instantly in your browser with no data sent to any server.
Frequently Asked Questions
How do I calculate what percentage one number is of another?
Divide the part by the whole and multiply by 100. For example, to find what percent 25 is of 200, compute (25 / 200) x 100 = 12.5%. Use the "X is what % of Y?" mode in the calculator above to get instant results.
What is the formula for finding a percentage of a number?
Multiply the number by the percentage and divide by 100. For example, 15% of 80 is (80 x 15) / 100 = 12. The "What is X% of Y?" mode handles this calculation automatically.
How do reverse percentage calculations work?
A reverse percentage finds the original value before a percentage increase or decrease was applied. If an item costs $120 after a 20% markup, the original price was $120 / 1.20 = $100. The third mode in this calculator handles both increase and decrease scenarios.
Can I use this calculator for percentage change between two values?
Yes. To find the percentage change, use the "X is what % of Y?" mode by entering the difference as X and the original value as Y. For example, if a price went from $50 to $65, the change is 15/50 = 30% increase.