Reverse Percentage Calculator

Use this reverse percentage calculator to work backwards from a final value and percentage change to find the original value.

Final Value
Percentage (%)
Final Value Is After

How to Use the Reverse Percentage Calculator

Enter the final value and percentage change to estimate the original value before the increase or decrease.

Practical Example

If a value after a 25% increase is 125, the original value is 100.

Factors That Affect the Result

The direction of change matters. An increase and a decrease of the same percentage are not exact opposites because they use different bases.

Frequently Asked Questions

Can I reverse a percentage increase?

Yes. Divide the final value by one plus the percentage as a decimal.

Can I reverse a percentage decrease?

Yes. Divide the final value by one minus the percentage as a decimal.

Why does subtracting the percentage not work?

Because the percentage change was calculated from the original value, not the final value.

Related Tools

Reverse Percentage Formulas

To reverse an increase of r%, divide the final value by 1 + r/100. To reverse a decrease, divide by 1 − r/100. These formulas recover the base value on which the original percentage change was calculated.

Why Subtracting the Percentage Fails

If 100 increases by 20%, the result is 120. Subtracting 20% from 120 gives 96, not 100, because that 20% is now calculated from 120. Reverse percentage calculations must divide by the original change multiplier instead.

Important Edge Cases

A 100% decrease reduces any starting value to zero, so a unique original value cannot be recovered from the final value alone. For decreases below 100%, use the decrease formula; for increases, use the increase formula and keep sufficient decimal precision before rounding.