Percentage Calculator
Variable Key
What is X% of Y?
Find the part given the percentage and the whole.
X is what % of Y?
Find the percentage given part and whole.
Percentage change
Measure relative increase or decrease.
Percentage of percentage
Compute a percentage of another percentage.
Increase / Decrease by %
Apply a percentage to change a value.
A percentage represents a ratio expressed as a fraction of 100. The word comes from Latin "per centum" meaning "by the hundred." Percentages are used everywhere: discounts, test scores, tax rates, nutrition labels, and statistics.
Tip: Mental math shortcut: 10% of any number = move the decimal left once. Then multiply for other percentages. 35% = 30% + 5% = (3 × 10%) + (10%/2).
- 1Identify what you are given: the part, the whole, or the percentage
- 2Use the formula: Percentage = (Part ÷ Whole) × 100
- 3Rearrange for what you need: Part = (P/100) × Whole
- 4Always double-check by verifying the part is less than the whole (unless > 100%)
Percentage over 100%
Perfectly valid. If a business grew from 100 to 250 employees, that's 150% growth.
Percentage of a percentage
To find 20% of 30%: multiply them. 0.20 × 0.30 = 0.06 = 6%. This is often confused with "20% + 30% = 50%".
| Percent | Fraction | Decimal |
|---|---|---|
| 10% | 1/10 | 0.1 |
| 12.5% | 1/8 | 0.125 |
| 20% | 1/5 | 0.2 |
| 25% | 1/4 | 0.25 |
| 33.3% | 1/3 | 0.333 |
| 40% | 2/5 | 0.4 |
| 50% | 1/2 | 0.5 |
| 60% | 3/5 | 0.6 |
| 66.7% | 2/3 | 0.667 |
| 75% | 3/4 | 0.75 |
| 80% | 4/5 | 0.8 |
| 100% | 1 | 1.0 |
Fun Fact
The percent sign (%) evolved from the Italian "per cento." By the 17th century, it was being written as "p100" or "p/100", which gradually became the % symbol we use today.
References