How to Calculate Percentage Decrease
Percentage decrease = (original − new) ÷ original × 100.
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Formula and worked example
Percentage decrease = (original − new) ÷ original × 100
From 120 to 90: the drop is 30. Divide 30 by the original 120 and multiply by 100 = 25%.
Apply a percentage decrease
Multiply by 1 − p/100. Reducing $75 by 20% gives 75 × 0.80 = $60. To recover an original value, divide by the remaining multiplier.
Common mistake
Use the original value as the baseline for relative change. A percentage calculation can give a different answer when the denominator changes.
Related percentage guides
Source & methodology
BLS documents the standard percent-change calculation using the earlier value as the denominator.