Math
Percentage Calculator: Master Percentages in Minutes
Learn how to calculate percentages, percentage change, and solve common percentage problems with easy formulas.
Percentages are everywhere: sales tax, tips, interest rates, test scores, and discounts. Understanding percentages is essential for everyday math.
What Is a Percentage?
A percentage is a fraction of 100. 25% means 25 out of 100, or 0.25 in decimal form. To convert: divide the percentage by 100.
Common Percentage Calculations
- What is X% of Y? Multiply: Y × (X/100). Example: 20% of $50 = $50 × 0.20 = $10
- X is what % of Y? Divide: (X/Y) × 100. Example: $10 is what % of $50? (10/50) × 100 = 20%
- Percentage change: ((New - Old) / Old) × 100. Example: $50 to $60 = (60-50)/50 × 100 = 20% increase
Percentage Increase vs Decrease
Percentage increase: result is positive. Percentage decrease: result is negative (or use Old - New for a positive number).
Tips and Discounts
For a 15% tip on $40: $40 × 0.15 = $6. For a 20% discount on $100: $100 × 0.20 = $20 off, final price $80.
Frequently Asked Questions
How do I calculate percentage increase?
Subtract the old value from the new value, divide by the old value, then multiply by 100. Formula: ((New - Old) / Old) × 100
What is the difference between percent and percentage point?
A percent is a relative change. A percentage point is an absolute change. If interest goes from 5% to 7%, that's a 2 percentage point increase, but a 40% increase.
How do I reverse a percentage?
If you know the final amount after a percentage was applied, divide by (1 + rate). Example: $120 after 20% increase = $120 / 1.20 = $100 original.