Percent Change Calculator
Enter where you started and where you finished. The percent change, the direction and the absolute difference all update as you type.
Percent change from one value to another
Direction
Decrease
Absolute difference
20
Percent change
-25%
(60 − 80) ÷ 80 × 100
The percent change formula
Percent change = (New − Old) ÷ |Old| × 100
A positive result is an increase. A negative result is a decrease. The sign is the whole point of percent change — it is the measure you use when one value came before the other.
Worked example — 80 falls to 60
60 − 80 = −20
−20 ÷ 80 = −0.25
−0.25 × 100 = −25
So 80 to 60 is a 25% decrease.
Why the formula uses the absolute starting value
Dividing by |old| rather than old matters as soon as negative numbers appear.
A business improving its result from −50 to −25 has got better. Dividing by the signed −50 would report that as a 50% decrease, which reads as bad news. Dividing by 50 reports a 50% increase, which is what actually happened.
Percent change against percent difference
- Percent change has a direction. It answers "how much did this move?" and divides by the starting value. Order matters.
- Percent difference has no direction. It answers "how far apart are these two?" and divides by their mean. Order does not matter.
Use percent change for a before and after. Use percent difference when neither value is the original — two measurements of the same thing, or two competing readings.
Change is not reversible
A move from 80 to 60 is a 25% decrease, but the move back from 60 to 80 is a 33.3% increase. The base changed. Never assume you can undo a percent change by applying the same percentage in reverse.
Common questions
- What is the percent change formula?
- Percent change = (new value − old value) ÷ |old value| × 100. A positive answer is an increase and a negative answer is a decrease.
- What is the difference between percent change and percent difference?
- Percent change has a direction: it measures a move from an old value to a new one and divides by the old value. Percent difference has no direction: it divides by the mean of the two values and gives the same answer whichever order you enter them.
- How do I calculate percent change with negative numbers?
- Divide by the absolute value of the starting number. Going from −50 to −25 is an improvement of 25 on a base of 50, so it is a 50% increase, not a 50% decrease.
- What does a percent change of more than 100% mean?
- An increase above 100% means the value more than doubled. A decrease cannot go below −100% unless the value crosses into negative numbers.