Percentage Increase / Decrease Calculator
Find the percentage increase or decrease between two values, plus the raw difference and which direction it moved.
How it works
Percentage change = (new − original) ÷ |original| × 100
The change is always measured against the original value, not the new one, so the base matters. A rise from 80 to 100 is a 25% increase, but the reverse — 100 back down to 80 — is only a 20% decrease, because the base is larger the second time. That asymmetry is why a 50% loss needs a 100% gain to recover.
Worked example
From 80 to 100 the change is 100 − 80 = 20. Divided by the original 80 that is 20 ÷ 80 = 0.25, or a 25% increase.
Sources: Percentage change — Wikipedia
Frequently asked questions
Why isn’t a 25% increase cancelled by a 25% decrease?
Because each percentage is taken from a different base. A 25% increase of 80 gives 100, but a 25% decrease of 100 gives 75 — the drop is calculated on the larger number, so you land below where you started.
How do I handle a decrease?
Enter the smaller number as the new value. The result comes out negative, which signals a percentage decrease. This tool labels the direction for you.
What if the original value is zero?
Percentage change from zero is undefined — any positive value is an “infinite” percentage increase — so a base of 0 is rejected. Use the absolute change instead.
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This calculator is for educational purposes. Double-check important results before acting on them.