Percentage Calculator
Calculate percentages three ways: find a percentage of a number, determine what percent one number is of another, or find the original value from a percentage result. Select the mode that matches your question.
Example: 20% of 150 = 30
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Example: 30 is what % of 150? Answer: 20%
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Example: 30 is 20% of what? Answer: 150
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Percentage Formulas Explained
All percentage problems are variations of one core relationship. Once you understand the formula, you can solve any percentage question.
Core Relationship
Mode 1: Find a Percentage of a Number
Used when you know the percentage and the whole, and need to find the part.
Example: 15% of 200 = (15 ÷ 100) × 200 = 30
Mode 2: What Percent is X of Y?
Used when you know both values and want to express their relationship as a percentage.
Example: 45 is what % of 180? = (45 ÷ 180) × 100 = 25%
Mode 3: Reverse Percentage (Find the Original)
Used when you know the result of a percentage calculation and need to find the original whole.
Example: 45 is 25% of what? = 45 ÷ 0.25 = 180
Everyday Uses of Percentage Calculations
Shopping Discounts
Find the actual savings when an item is 30% off. Mode 1: 30% of $80 = $24 off.
Exam Scores
A student scored 72 out of 90. Mode 2: (72 ÷ 90) × 100 = 80%.
Tax Calculations
Find total price before tax. If $118 includes 18% tax, Mode 3: original = 118 ÷ 1.18 = $100.
Finance & Investment
Calculate interest earned or return on investment as a percentage of the principal amount.
Nutrition Labels
Find how much of your daily intake one meal covers. Mode 2: 600 ÷ 2000 × 100 = 30%.
Commission & Tips
Calculate a 15% tip on a $65 bill. Mode 1: 15% of 65 = $9.75.
Quick Reference: Common Percentages of 100
| Percentage | Fraction | Decimal | Value of 100 |
|---|---|---|---|
| 1% | 1/100 | 0.01 | 1 |
| 5% | 1/20 | 0.05 | 5 |
| 10% | 1/10 | 0.10 | 10 |
| 20% | 1/5 | 0.20 | 20 |
| 25% | 1/4 | 0.25 | 25 |
| 33.33% | 1/3 | 0.333 | 33.33 |
| 50% | 1/2 | 0.50 | 50 |
| 75% | 3/4 | 0.75 | 75 |
Frequently Asked Questions
How do I calculate a percentage manually?
Multiply the number by the percentage, then divide by 100. For example, 12% of 250 = (12 × 250) ÷ 100 = 30. Or move the decimal two places left: 12% = 0.12, then 0.12 × 250 = 30.
What is a reverse percentage?
A reverse percentage finds the original value before a percentage was applied. For instance, if a price after a 20% discount is $80, the original price was $80 ÷ 0.80 = $100.
Can percentages be more than 100%?
Yes. A value that is 150% of another is one and a half times greater. Percentages above 100 are common in growth calculations, markup pricing, and comparisons between quantities.
Why does this tool show three separate modes?
Percentage questions come in three forms depending on which value is unknown. Separating them into clear modes removes confusion and helps you get accurate results for your specific question without manual formula lookup.