Percentage Calculator
Calculate percentage increases, decreases, discounts, and ratios instantly with our free online percentage tool.
How to Calculate Percentages
Percentages represent a part of a whole expressed as a fraction of 100. Understanding how to calculate percentages is essential for finance, shopping discounts, statistics, and everyday math.
What is X% of Y? → (X ÷ 100) × Y
% Change → ((New − Old) ÷ Old) × 100
Step-by-Step Example:
Let's calculate what is 20% of 150:
- Convert 20% to a decimal: 20 ÷ 100 = 0.20
- Multiply by the number: 0.20 × 150 = 30
- Therefore, 20% of 150 is 30.
Common Percentage Reference
Quick reference table for common percentage calculations based on a value of 100:
| Percentage | Decimal | Fraction | Of 100 | Of 500 |
|---|---|---|---|---|
| 5% | 0.05 | 1/20 | 5 | 25 |
| 10% | 0.10 | 1/10 | 10 | 50 |
| 15% | 0.15 | 3/20 | 15 | 75 |
| 20% | 0.20 | 1/5 | 20 | 100 |
| 25% | 0.25 | 1/4 | 25 | 125 |
| 50% | 0.50 | 1/2 | 50 | 250 |
| 75% | 0.75 | 3/4 | 75 | 375 |
| 100% | 1.00 | 1/1 | 100 | 500 |
Frequently Asked Questions
How do I calculate a percentage increase?
Use the formula: ((New Value − Original Value) ÷ Original Value) × 100. For example, if a price goes from $80 to $100, the increase is ((100 − 80) ÷ 80) × 100 = 25%.
How do I calculate a discount percentage?
To find the discount amount, multiply the original price by the discount percentage divided by 100. For a 20% discount on $150: 150 × 0.20 = $30 discount. The final price is $120.
What is the easiest way to calculate percentages mentally?
For 10%, simply move the decimal point one place to the left. For 5%, take half of 10%. For 20%, double 10%. For 50%, divide by 2. These building blocks make mental math much faster.