Percentage Calculator
Percentages, changes & comparisons
How to Use the Percentage Calculator
Our percentage calculator handles three common percentage calculations: finding a percentage of a number, determining what percentage one number is of another, and calculating the percentage change between two values.
Three Calculation Modes
- What is X% of Y? Find a portion of a number (e.g., what is 20% of 150?)
- X is what % of Y? Determine the percentage relationship between two numbers
- % change from X to Y: Calculate the percentage increase or decrease between values
Master all types of percentage math with our Complete Guide to Percentage Calculations.
Common Uses
Percentage calculations are essential for discounts, tips, taxes, grades, statistics, and financial analysis. Understanding percentages helps with budgeting, shopping, and making informed decisions.
Quick Mental Math Tips
- To find 10%, move the decimal point one place left
- To find 1%, move the decimal point two places left
- 50% is simply half the number
- 25% is one quarter of the number
Frequently Asked Questions
Multiply the number by the percentage, then divide by 100. For 15% of 200: 200 x 15 / 100 = 30. Or convert percentage to decimal (15% = 0.15) and multiply: 200 x 0.15 = 30.
Formula: ((New Value - Old Value) / Old Value) x 100. If price went from $50 to $65: ((65-50)/50) x 100 = 30% increase. If it dropped to $40: ((40-50)/50) x 100 = -20% decrease.
Divide the part by the whole, then multiply by 100. What percentage is 25 of 200? (25/200) x 100 = 12.5%. This calculation is useful for grades, discounts, and proportions.
If something costs $85 after 15% off, original price = final price / (1 - discount). $85 / (1 - 0.15) = $85 / 0.85 = $100 original price. This helps find prices before discounts or taxes.
To add 20% to 150: 150 x 1.20 = 180 (or 150 + 150x0.20). To subtract 20%: 150 x 0.80 = 120 (or 150 - 150x0.20). The multiplier is (1 + percentage) for adding, (1 - percentage) for subtracting.
Percentages help understand discounts, tips, taxes, interest rates, nutritional info, grades, and statistical data. Knowing that a 20% off $50 item saves $10, or a 7% sales tax adds $3.50, enables better financial decisions.