Reverse Percentage Calculator
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Find the original value before a percentage increase or decrease was applied. Simple, fast, and accurate.
Find the original value before a percentage increase or decrease was applied. Simple, fast, and accurate.
A reverse percentage calculation works backwards from a final value to find the original value before a percentage increase or decrease was applied. For example, if a price is now £120 after a 20% increase, the reverse percentage tells you the original price was £100. It is especially useful for finding pre-tax prices, original sale prices, and pre-discount costs.
The method depends on whether the percentage was an increase or a decrease:
If the value increased:
Formula: Original = Final ÷ (1 + Percentage ÷ 100)
If the value decreased:
Formula: Original = Final ÷ (1 − Percentage ÷ 100)
Example 1 — After an increase
A price is £120 after a 20% increase. What was the original price?
120 ÷ 1.20 = £100
Example 2 — After a decrease
A price is £80 after a 20% decrease. What was the original price?
80 ÷ 0.80 = £100
Example 3 — After an increase
A salary is £150 after a 50% increase. What was the original salary?
150 ÷ 1.50 = £100
What is a reverse percentage?
It is a calculation that works backwards — given a final value and the percentage that was
applied to it, it finds the original value before the percentage change took place.
Why can't I just subtract the percentage directly?
Because the percentage was applied to the original value, not the final value. For example,
if a price rose 20% to £120, subtracting 20% of £120 gives £96 — which is wrong.
The correct original is £100. You must divide by the percentage factor instead.
Can the percentage be more than 100%?
Yes. For example, if a value increased by 150%, you divide the final value by 2.5 to find the original.
What if the percentage is 100% decrease?
A 100% decrease would mean the final value is zero, making the original impossible to recover.
The calculation is undefined in this case.