How do I find the original value before a percentage decrease?

Divide the final value by the remaining percentage. For example, if 80 is after a 20% decrease, divide 80 by 0.8 to get the original 100.

How do I reverse a percentage increase?

Divide the final value by the increased multiplier. For example, if 120 is after a 20% increase, divide 120 by 1.2 to get the original 100.

When should I use a reverse percentage calculator?

Use it when you know the final number and the percentage change, but you need to recover the starting amount before the increase or decrease happened.

Reverse percentage calculator

Reverse Percentage Calculator

Use this reverse percentage calculator to recover the original value before a percentage increase or decrease was applied. It shows the original value and the size of the change in money or units.

Original value

100

If 80 is after a 20% decrease, the original value was 100 and the change amount was 20.

Change amount

Final amount

How it works

Work backward from the final number

A reverse percentage calculator starts from the final amount and the known percentage change. It divides by the right multiplier to recover the number that existed before the increase or decrease happened.

Formula

original = final ÷ (1 ± percentage)

Use 1 - percentage when the final number came after a decrease, and 1 + percentage when it came after an increase.

Worked example

1. Start with a final amount of 80.
2. The 20% change is a decrease, so the remaining multiplier is 0.8.
3. Divide 80 by 0.8.
4. The original value was 100.

When people use this

Discounts: recover the original price before the sale.
Tax: estimate the pre-tax amount when you know the final total.
Growth: work back to the starting value before an increase.
Reports: reverse a known percentage movement to recover the baseline figure.

Related calculators

Keep moving through the percentage cluster

Reverse percentage fits naturally beside discount and tax pages because those tools often give you a final number first. It also pairs with the increase and decrease calculators when you want to move backward instead of forward.

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