Percent Change Calculator
Calculate the percent change from an old value to a new one, the absolute difference, and the percentage needed to get back to where you started.
Percent change tells you how big a change is relative to where you started. It is the standard way to compare price rises, pay increases, sales growth or a drop in website traffic, because a change of 20 means something very different on a base of 80 than on a base of 8,000. Enter the old and new values to get the percentage, the raw difference and the change you would need to reverse it.
How to use this tool
- Enter the original (old) value.
- Enter the new value.
- Read the percent change: positive means an increase, negative a decrease.
- Check "Change needed to return to the old value" to see what it takes to undo the move.
Formula
Percent change = (new − old) ÷ |old| × 100
The old value is the base, so the order matters: swapping old and new gives a different percentage. Dividing by the absolute value of the old value keeps the sign meaningful when the starting value is negative, such as a loss shrinking to a smaller loss.
Example
A phone plan goes from $80 to $100 a month. The change is 100 − 80 = $20, and 20 ÷ 80 × 100 = +25%. To get back from $100 to $80 the price would have to fall by 20 ÷ 100 = 20%, not 25%, because the base is now larger.
Frequently asked questions
What is the difference between percent change and percent difference?
Percent change has a direction: it measures from an old value to a new one. Percent difference compares two values with no starting point and divides the gap by their average, so 80 and 100 differ by about 22.2%.
Can percent change be more than 100%?
Yes, for increases: going from 50 to 150 is +200%. For positive values a decrease cannot go below −100%, which means the value fell all the way to zero.
Why can’t I calculate a change from zero?
Any increase from 0 is infinitely large relative to 0, so the percentage is undefined. Report the absolute change instead, or measure from the first non-zero value.
How do I combine two percent changes?
Multiply the growth factors rather than adding the percentages. A 10% rise followed by a 10% fall is 1.10 × 0.90 = 0.99, a net decrease of 1%.
Last updated: 2026-10-30