Which percentage calculation answers my question?
Choose Percent of to find a portion, What percent to compare a part with its total, Change to compare an old value with a new value, or Find the whole when you know the part and its percentage. Selecting the right question avoids mixing up percentage change and percentage points.
Percentage of calculator: find a percent of any number
Use Percent of for a portion of a number, What percent for a part-to-whole comparison, Change for relative growth, or Find the whole to reverse a percentage.
Three useful formulas
Percent of: (X ÷ 100) × Y
What percent: (X ÷ Y) × 100
Change: ((New − Old) ÷ Old) × 100
Percentage increase calculator example: from 80 to 100
The increase is 20. Divide 20 by the starting value of 80 and multiply by 100: the percentage increase is 25%.
Percent and percentage points differ
Moving from 10% to 15% is an increase of 5 percentage points, or a 50% relative increase. A zero starting value has no defined percentage change. This tool requires a positive starting value for a meaningful increase/decrease label.
Choose the right percentage calculation
| Question | Mode | Example |
|---|---|---|
| 20% of 150 | Percent of | 30 |
| 45 is what percent of 150? | What percent | 30% |
| 80 increases to 100 | Change | 25% increase |
| 30 is 20% of what? | Find the whole | 150 |
The denominator defines the question
Percentage change compares with the starting value. A percentage-point difference subtracts two percentages. Neither is interchangeable with the other; label the result before using it in a report.
Key terms explained
- Base
- The whole or starting value used as the denominator.
- Percentage point
- An absolute difference between two percentages.
- Relative change
- A change divided by the starting value.