How this calculator works
Subtract the initial measurement from the final measurement, then divide by the initial measurement. The decimal ratio and percentage are two notations for the same relative change. This calculator keeps the signed initial baseline, including negative values. Interpret negative-baseline results carefully because their signs may not match everyday language about improvement.
Formula
Absolute change = final - initial. Relative change = (final - initial)/initial. Percentage change number = 100 × relative change.
Worked example
From 80 to 100, the absolute change is 20 and the relative change is 0.25, or 25%. Reversing the comparison gives -20/100 = -0.2, or -20%.
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Frequently asked questions
Why does reversing the comparison change the magnitude?
The initial value is the denominator. Reversing the values changes that baseline.
What convention is used for negative initial values?
The denominator is the signed initial value. For -100 to -50 this gives -0.5 even though the final number is larger.
Can I compare values with different units?
Convert them to the same unit first. Relative change only has meaning when both measurements describe the same quantity.