Percentage Change Calculator Guide: Formula & Worked Example
Short answer
Percent increase or decrease between two values. In the fixed example below, percent increase is 25%. Your answer depends on the inputs and assumptions you choose.
Formula
Change = (New − Old) / |Old| × 100
Use the relationship above with consistent units. The inputs are old value, new value. Use the input scale shown beside each field and keep time periods and units consistent. Only round the final result for display.
Worked example
- Old value
- 80
- New value
- 100
- Percent increase: 25%
- Difference: 20
- Percent difference: 22.2222%
Understanding the result
Percent increase or decrease between two values. Start with the base example, then replace each value with the figure that matches your situation.
Old value
The example uses 80 for old value. This is an illustration, not a recommended value. Keep the unit and time period shown by the field.
New value
The example uses 100 for new value. This is an illustration, not a recommended value. Keep the unit and time period shown by the field.
What the comparison means
The comparison changes only old value, keeping every other example input fixed. This isolates that input's effect on the primary result. It does not predict future outcomes.
Check units, date boundaries and rounding before using the answer in a report or a practical measurement.
Comparison
| Scenario | Input | Result |
|---|---|---|
| Lower input | Old value: 64 | Percent increase: 56.25% |
| Base example | Old value: 80 | Percent increase: 25% |
| Higher input | Old value: 96 | Percent increase: 4.1667% |
Common mistakes
- Using the wrong units for old value.
- Comparing results while changing more than one input at a time.
- Check units, date boundaries and rounding before using the answer in a report or a practical measurement.
Checklist
- Confirm old value.
- Confirm new value.
- Check the result against your source or provider.
Calculators Percentage Editorial Team
Calculator guides from the Calculators Percentage team. These introductory examples are educational, not professional advice.
Last reviewed:
Check units, date boundaries and rounding before using the answer in a report or a practical measurement.