Reverse Percentage Calculator
Work backwards: find the price before a discount or tax, or the whole from a part.
%
—Original value
—Amount of the change
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How it works
A common mistake is to subtract the percentage from the final value: 120 − 20% = 96, but the price before a 20% increase was 100. The right formula divides: original = final ÷ (1 + p ÷ 100) after an increase, final ÷ (1 − p ÷ 100) after a decrease, and part ÷ (p ÷ 100) to find the whole.
FAQ
Why isn't it just 120 − 20%?
Because the 20% was calculated on the original price (100), not on 120. 20% of 120 is 24, 20% of 100 is 20.