Percentage Change Calculator
Old value to new value, with the absolute difference shown alongside so the direction is never ambiguous.
Change
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Absolute difference
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Direction
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Worked example
From 80 to 100 is +25%, not +20%. The base is the old value, so a 20-point rise on a base of 80 is a quarter of the starting figure.
Percentage change is always relative to the starting value, and that base is what people get wrong. A rise from 80 to 100 is 25%; a fall from 100 to 80 is 20%. Same 20 points, different percentages, because the denominators differ.
Negative starting values
When the old value is negative, dividing by it flips the sign and produces nonsense — a company going from −£10m to −£5m is improving, but the raw formula reports −50%. This calculator divides by the absolute value so the direction stays correct.