Calculate the percentage increase or decrease between two values. Enter any two of three fields — initial value, final value, or percentage — and the third is computed automatically.
How to Calculate Percentage Increase
Formula: (Final − Initial) / Initial × 100
Example: A salary rises from $4,000 to $4,600.
- Change: 4,600 − 4,000 = 600
- Percentage increase: 600 / 4,000 × 100 = 15%
How to Calculate Percentage Decrease
Formula: (Initial − Final) / Initial × 100
Example: A product price drops from $80 to $68.
- Change: 80 − 68 = 12
- Percentage decrease: 12 / 80 × 100 = 15%
Reverse Calculation
Fill in any two fields and the third is computed automatically.
Percentage Increase — all three directions:
- Initial + Final → Percentage increase
- Initial + Percentage → Final value:
Final = Initial × (1 + % / 100)
- Final + Percentage → Initial value:
Initial = Final / (1 + % / 100)
Percentage Decrease — all three directions:
- Initial + Final → Percentage decrease
- Initial + Percentage → Final value:
Final = Initial × (1 − % / 100)
- Final + Percentage → Initial value:
Initial = Final / (1 − % / 100)
Percentage Increase vs Percentage Decrease
These two calculations are not symmetric. Starting from 100:
- A 25% increase gives 125
- A 25% decrease from 125 gives 93.75, not 100
This is because the base changes. Always use the correct mode and enter the actual starting value.
Frequently Asked Questions
What is the formula for percentage increase?
Percentage increase = (Final Value − Initial Value) / Initial Value × 100. For example, if a price rises from 80 to 100, the increase is (100 − 80) / 80 × 100 = 25%.
What is the formula for percentage decrease?
Percentage decrease = (Initial Value − Final Value) / Initial Value × 100. For example, if a price drops from 100 to 80, the decrease is (100 − 80) / 100 × 100 = 20%.
Can I find the original value if I know the final value and the percentage?
Yes. In Increase mode: Initial = Final ÷ (1 + Percentage / 100). In Decrease mode: Initial = Final ÷ (1 − Percentage / 100). Fill in any two of the three fields and the calculator computes the third.
What is the difference between percentage increase and percentage decrease?
Both compare two values, but the denominator is always the initial value and the direction differs. A 25% increase from 80 gives 100, while a 20% decrease from 100 gives 80. Note that these are not symmetric — a 25% increase followed by a 25% decrease does not return to the starting value.
Why are percentage increase and percentage decrease not symmetric?
Because both use the initial value as the base. Going from 100 to 125 is a 25% increase. Going back from 125 to 100 is a 20% decrease (not 25%), because the base is now 125. This asymmetry is why you should use the correct mode for your starting point.