Percentage Calculator
Calculate percentages quickly and accurately. Find what percent of a number is, determine what percentage one number is of another, or compute the percentage change between two values.
Three calculation modes for all common percentage problems
Calculate Percentage
The percentage to calculate (e.g., 25)
The number to find the percentage of (e.g., 200)
How to Use This Percentage Calculator
Choose a Mode
Select one of three calculation modes: find X% of Y, determine what percent X is of Y, or calculate percentage change between two values.
Enter Your Numbers
Type the values into the two input fields. The labels adjust automatically based on the mode you selected.
Get Your Result
Click Calculate or press Enter to see the answer, along with the step-by-step formula used to compute it.
Percentage Formulas Explained
Result = (Percentage / 100) x TotalAll percentage calculations are based on three core relationships between a part, a whole, and a percentage.
1. What is X% of Y?
Result = (X / 100) x YExample: 15% of 200 = (15 / 100) x 200 = 30
2. X is what % of Y?
Percentage = (X / Y) x 100Example: 30 is what % of 200? = (30 / 200) x 100 = 15%
3. Percentage Change
Change = ((New - Old) / |Old|) x 100Example: Change from 80 to 100 = ((100 - 80) / 80) x 100 = 25% increase
Key points to remember:
- To convert a percentage to a decimal, divide by 100 (e.g., 25% = 0.25)
- To convert a decimal to a percentage, multiply by 100 (e.g., 0.75 = 75%)
- Percentage change can be negative, indicating a decrease from the original value
- Division by zero is undefined, so the whole/original value cannot be zero
Common Percentage Reference
| Percentage | Decimal | Fraction | % of 100 |
|---|---|---|---|
| 5% | 0.05 | 1/20 | 5 |
| 10% | 0.10 | 1/10 | 10 |
| 15% | 0.15 | 3/20 | 15 |
| 20% | 0.20 | 1/5 | 20 |
| 25% | 0.25 | 1/4 | 25 |
| 33.33% | 0.3333 | 1/3 | 33.33 |
| 50% | 0.50 | 1/2 | 50 |
| 75% | 0.75 | 3/4 | 75 |
| 100% | 1.00 | 1/1 | 100 |
| 150% | 1.50 | 3/2 | 150 |
Frequently Asked Questions
How do I calculate what percent of a number something is?
To find X% of Y, convert the percentage to a decimal by dividing by 100, then multiply by the number. For example, 25% of 200: (25 / 100) x 200 = 50. This is the most common percentage calculation, used for tips, discounts, tax amounts, and more.
How do I find what percentage one number is of another?
Divide the part by the whole, then multiply by 100. For example, to find what percentage 30 is of 120: (30 / 120) x 100 = 25%. This is useful for calculating grades, completion rates, and proportions.
What is the formula for percentage change?
Percentage change = ((New Value - Old Value) / |Old Value|) x 100. A positive result means an increase, and a negative result means a decrease. For example, if a price went from $80 to $100: ((100 - 80) / 80) x 100 = 25% increase.
What is the difference between percentage change and percentage difference?
Percentage change measures the change relative to the original value (directional - increase or decrease). Percentage difference measures the difference relative to the average of both values (non-directional). This calculator computes percentage change, which is more commonly used for price changes, growth rates, and comparisons over time.
Can percentages be greater than 100%?
Yes. A percentage greater than 100% simply means the value exceeds the reference amount. For example, 150% of 40 is 60 (more than 40), and if a stock price rises from $10 to $25, that is a 150% increase. Percentage change results commonly exceed 100% when values double or more.
About This Calculator
This percentage calculator is provided for general informational and educational purposes. Results are computed using standard mathematical formulas and are suitable for everyday use including calculating tips, discounts, tax amounts, grade percentages, and growth rates. For financial, scientific, or legal calculations where precision is critical, verify results with a qualified professional.