Percentage Calculator
Calculate percentages, find values based on percentages, and determine percentage changes with this simple calculator.
Percentage Calculator
Select Calculation Method
Understanding Percentages
A percentage represents a portion of a whole, with the whole being 100%. The term "percent" comes from "per centum," which means "per hundred" in Latin. Percentages are used widely in statistics, finance, and everyday calculations.
Common Uses for Percentages
Shopping
Calculate discounts, sales tax, and price changes when shopping.
Finance
Determine interest rates, investment returns, and price inflation.
Statistics
Express data proportions, probabilities, and comparison metrics.
Education
Calculate grade percentages, test scores, and academic progress.
Converting Between Forms
Percentages, decimals, and fractions are different ways of expressing the same values:
- Decimal to Percentage: Multiply by 100 and add % symbol (0.25 → 25%)
- Percentage to Decimal: Divide by 100 and remove % symbol (25% → 0.25)
- Fraction to Percentage: Divide numerator by denominator, multiply by 100 (1/4 → 25%)
- Percentage to Fraction: Express as a fraction over 100, then simplify (25% → 25/100 → 1/4)
Quick Tip: Mental Percentage Calculations
To quickly calculate 10% of a number, simply move the decimal point one place to the left. For 20%, calculate 10% and double it. For 25%, find 100% ÷ 4.
Frequently Asked Questions
How do I calculate sales tax using percentages?
To calculate sales tax, use the "Find Value" option. Enter the tax rate as the percentage and the pre-tax price as the total value. The calculator will show the tax amount. For the final price, add this amount to the original price.
How do I find what percentage one number is of another?
Use the "Find Percentage" option. Enter the first number as the value and the second number as the total. For example, to find what percentage 25 is of 200, enter 25 as the value and 200 as the total. The result is 12.5%.
How do I calculate a percentage increase or decrease?
Use the "Percentage Change" option. Enter the original value and the new value. The calculator will determine whether it's an increase or decrease and by what percentage. For example, a change from 100 to 120 is a 20% increase.
Why does the percentage change formula use the absolute value of the original number?
The absolute value is used to ensure that the direction of change (increase or decrease) is accurately represented for negative values. This maintains the convention that a positive percentage change means an increase, while a negative percentage change means a decrease.
Can I calculate compound percentage changes?
Yes, but you need to do it in steps. If you have multiple percentage changes (like 5% followed by 10%), you can't simply add them. Instead, apply each percentage change to the result of the previous calculation to get the accurate final result.
How accurate are the percentage calculations?
Our percentage calculator maintains high precision internally and displays results rounded to 2-4 decimal places as appropriate. For fractions, we identify common fractions where possible, but very complex ratios are displayed as decimals.
Need More Calculation Tools?
Explore our full range of utility calculators to simplify your everyday calculations.