PercentLab

Percent Increase / Decrease

Positive change vs. negative change — both sides.

Original

New

Increase %

Decrease %: -25

What you entered

Original: 80New: 100

1
Difference
100 − 80= 20
2
As a % increase over the original
(20 ÷ 80) × 100= 25%
3
As a % decrease framing (reverse direction)
((80 − 100) ÷ 80) × 100= -25%

Result

Increase %: 25

From 80 to 100 is a 25% increase.

Percent increase and the decrease needed to reverse it

The increase column measures the rise from the first value. The decrease column shows the fall from the second back to the first.

From	To	Increase	Decrease to reverse
100	120	20.00%	-20.00%
80	100	25.00%	-25.00%
200	260	30.00%	-30.00%
100	150	50.00%	-50.00%
50	75	50.00%	-50.00%
40	60	50.00%	-50.00%

This calculator reports the decrease as the mirror of the increase, both measured against the same original value - so a 50% increase is paired with a -50% decrease. That is not the same as the percentage fall needed to get back to the starting figure, which is always smaller because it is measured against the larger number: going from 100 to 150 is a 50% rise, but 150 back to 100 is a 33.3% fall. If you need that recovery figure, use the percentage change calculator with the values in the reverse order.

Two framings of the same move

Going from 80 to 100 is a 25% increase, but going back from 100 to 80 is only a 20% decrease — the percentages aren't symmetric because the base you're dividing by changes direction.

Where this trips people up

Sale prices are the classic trap: a 50% price increase followed by a 50% decrease does NOT return you to the original price — it leaves you 25% below it.

Frequently asked questions

A product was $80, now it's $100 — is that a 20% or 25% increase?

It's a 25% increase. Percent increase = ((100 − 80) / 80) × 100 = 25%. The common mistake is dividing by the new value (which would give 20%), but you always divide by the original.

How is percent increase different from percent change?

Percent increase and decrease are just the positive and negative sides of percentage change. When the new value is larger, you have a percent increase; when smaller, a decrease. The percentage change calculator handles both in one tool.

Why isn't a 50% increase followed by a 50% decrease the same as no change?

Because the base changes. Starting at $100: a 50% increase gives $150. Now a 50% decrease is 50% of $150 = $75, not the original $100. You end up 25% below where you started. The asymmetry exists because the percentage is applied to a different base each time.

How do I find the original price if I know the final price after a percent increase?

Divide by (1 + rate/100). If something costs $150 after a 25% increase, the original was $150 / 1.25 = $120. This reversal is called 'finding the base' and trips up many students who try to subtract the percentage instead.