Percentage Calculator
How to Use
Select a calculation type, enter two values, and see the result instantly. Three modes are available: percentage of a number, what percentage one number is of another, and percentage change between two values.
What is Percentage Calculation?
A percentage expresses a number as a fraction of 100. Percentage calculations are among the most commonly used math operations in daily life, from calculating discounts and taxes to understanding statistics and financial returns. The word 'percent' comes from the Latin 'per centum,' meaning 'by the hundred.' This tool supports three essential percentage operations, making it easy to solve the most frequent percentage questions without a formula.
Formulas
X% of Y = (X / 100) × Y. X is what % of Y = (X / Y) × 100. % change = ((New − Old) / |Old|) × 100.
Common Use Cases
- Shopping discounts — calculate the final price after a percentage discount
- Tax calculation — determine tax amounts based on percentage rates
- Grade calculation — convert scores to percentages for academic grading
- Statistics — express proportions and ratios as percentages for easier comparison
- Investment returns — calculate percentage gains or losses on investments
Tips
When calculating percentage change, the direction matters — a 50% increase followed by a 50% decrease does not return to the original value. For example, 100 increased by 50% is 150, but 150 decreased by 50% is 75. To reverse a percentage increase of X%, the required decrease is X / (1 + X/100) × 100%. Keep this asymmetry in mind when working with financial data or comparing growth rates.
Privacy
All processing happens in your browser. No data is sent to any server.
FAQ
What is the difference between "X% of Y" and "percentage change"?
"X% of Y" finds the actual value of a percentage of a number ((X/100)×Y). Percentage change expresses the increase or decrease from one value to another as a percent (((New−Old)/|Old|)×100) and is signed depending on whether the value rose or fell. Pick the mode that matches your goal.
Are the numbers I enter sent to a server?
No. All calculations run entirely in your browser, and the values you enter are never sent to or stored on a server. You can safely compute figures like revenue or salaries.
Do a 50% increase and a 50% decrease cancel out?
No. Increasing 100 by 50% gives 150, but decreasing that 150 by 50% gives 75, not the original. To undo an X% increase, you need a decrease of X/(1+X/100)×100%. Keep this asymmetry in mind for financial or growth calculations.
Can it handle decimals, negatives, or division by zero?
It handles inputs with decimals and negative numbers. However, if Y is 0 in "X is what % of Y," or the old value is 0 in percentage change, the result is division by zero and not meaningful.
Which mode do I use to find a price after a discount?
Use "X% of Y" to find the discount amount, then subtract it from the original price. For a 20% discount on $30, compute 20% × 30 = $6, then $30 − $6 = $24 as the final price.