Percentage Calculator
Calculate percentages easily. Find what percent of a number, calculate percent change, increase or decrease by a percentage, and more.
What is X% of Y?
X is what % of Y?
Percent Change
Increase/Decrease by %
Common Percentage Reference
| Fraction | Decimal | Percentage |
|---|---|---|
| 1/2 | 0.5 | 50% |
| 1/3 | 0.333 | 33.3% |
| 1/4 | 0.25 | 25% |
| 1/5 | 0.2 | 20% |
| 1/8 | 0.125 | 12.5% |
| 1/10 | 0.1 | 10% |
| 3/4 | 0.75 | 75% |
| 2/3 | 0.667 | 66.7% |
Percentage Basics
What is a Percentage?
A percentage is a number expressed as a fraction of 100. The word comes from Latin "per centum" meaning "by the hundred." 25% means 25 out of 100, or 0.25 as a decimal.
Converting Percentages
To decimal: Divide by 100 (25% = 0.25)
To fraction: Put over 100 (25% = 25/100 = 1/4)
From decimal: Multiply by 100 (0.25 × 100 = 25%)
Quick Mental Math
10%: Move decimal left one place
1%: Move decimal left two places
50%: Divide by 2
25%: Divide by 4
Frequently Asked Questions
How do I calculate a percentage of a number?
Formula: X% of Y = Y × (X/100)
Example: What is 20% of 150?
150 × (20/100) = 150 × 0.20 = 30
How do I calculate percent change?
Formula: ((New - Original) / Original) × 100
Example: From 100 to 125:
((125 - 100) / 100) × 100 = 25% increase
How do I increase/decrease by a percentage?
Increase: Value × (1 + Percent/100)
Decrease: Value × (1 - Percent/100)
Example: 100 increased by 15%:
100 × 1.15 = 115
Quick mental math for percentages
- 10%: Move decimal one place left (150 → 15)
- 1%: Move decimal two places left (150 → 1.5)
- 50%: Divide by 2 (150 → 75)
- 25%: Divide by 4 (150 → 37.5)
- 20%: Divide by 5 (150 → 30)
- 5%: Half of 10% (150 → 7.5)