FREE CALCULATOR · CHANGE

Reverse Percentage Calculator

Got the final price after tax, or the salary after a raise, and need the original? Reversing a percentage is trickier than it looks — you cannot just subtract the rate. This calculator does the correct backward math.

How the reverse percentage calculator works

Got the final price after tax, or the salary after a raise, and need the original? Reversing a percentage is trickier than it looks — you cannot just subtract the rate. This calculator does the correct backward math.

The formula

reverse increase: final ÷ (1 + rate ÷ 100) · reverse decrease: final ÷ (1 − rate ÷ 100)

Worked example

You paid $132 after a 10% increase. Divide 132 by 1.10 to get $120 — the original price. (Simply subtracting 10% from $132 would wrongly give $118.80.)

Where this comes in handy

Receipts: find the pre-tax subtotal from the total you paid.
Pay: recover your original salary from the post-raise figure.
Sales: find the list price behind a "20% off" ticket price.
Statistics: back out the baseline behind a reported increase.

Reverse Percentage Calculator — frequently asked questions

Why can't I just subtract the percentage from the final value?

Because the percentage was calculated on the original, smaller value. Subtracting 20% from 120 removes 24, but the original increase only added 20 to 100.

How do you reverse a percentage increase?

Divide the final value by 1 plus the rate as a decimal. To undo a 25% increase, divide by 1.25.

How do you reverse a percentage decrease?

Divide the final value by 1 minus the rate as a decimal. To undo a 25% decrease, divide by 0.75.

What is a common real-world use?

Finding pre-tax prices from receipts and original salaries from post-raise pay — anywhere the starting number was never shown to you.

Does this work for compound changes?

For a single change, yes. For multiple compounded changes, divide by each factor in turn — or use the compound growth calculator.