Education
Percentage Increase Calculator
Enter the original and new values. We compute the percentage change, the absolute change, and the multiplier — works for both increases and decreases.
The starting number — the “before” value. · e.g. 80
The ending number — the “after” value. · e.g. 100
Formula
((new − old) / |old|) × 100
Negative results mean a decrease. We divide by the absolute value of old so the sign of the change still reads naturally when the original is negative.
Percentage increase
+25%
80 → 100 (+20)
Examples
80 → 100
+25% increase · ×1.25
100 → 80
−20% decrease · ×0.80
50 → 75
+50% increase · ×1.5
200 → 150
−25% decrease · ×0.75
How it works
Percentage change tells you how much a value has grown or shrunk relative to its starting point.
% change · ((new − old) / |old|) × 100
multiplier · new / old
A positive result is an increase, a negative result is a decrease. A multiplier of 1 means no change; 2 means doubling; 0.5 means halving.
Frequently asked questions
Percentage change = ((new − old) / old) × 100. A positive result is an increase, a negative result is a decrease. We divide by the absolute value of the original so the sign of the result reads naturally even when the starting value is negative.
Percent change from zero is mathematically undefined — there's no baseline to compare against. Any non-zero new value would represent “infinite” percent change. We flag this case rather than printing a misleading number; report the absolute change instead.
If a rate goes from 4% to 6%, that's a 2 percentage point increase, but a 50% relative increase. Use percentage points when comparing two rates or proportions; use percentage change for everything else (prices, populations, scores, weights, etc.).
Yes — mathematically they're the same calculation. We label the result “increase” for positive change and “decrease” for negative change so the meaning is unambiguous, but a 20% decrease and a −20% increase are the same thing.
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