Percentage Change Calculator
Percentage change is a difference divided by a starting point. That denominator is where almost every mistake lives — including the one that makes a 90% collapse look recoverable.
Percentage change
25.00%
- Absolute change
- 20
- Growth factor (new / original)
- 1.25
- Change needed to return to the start
- -20.00%
Values update as you type. This calculator covers the single scenario its formula assumes — see Common Mistakes for what it leaves out.
The formula this calculator uses
Percentage Change = (New Value - Original Value) / Original Value x 100
- Vn
- New value — where you ended up
- V0
- Original value — where you began, and the divisor
- Vn - V0
- Absolute change, before conversion to a rate
- Vn / V0
- Growth factor — a 1.25 multiple is the same fact as +25%
How to check the result by hand
- 1
Identify the original value — not simply the smaller one
The original is whichever value came first in time. Using the smaller number as the divisor because it feels like a base gives results that reverse direction depending on whether you are describing growth or decline.
- 2
Subtract to get the absolute change
New minus original. Keep the sign: negative means the quantity fell. For 80 to 100 that is +20.
- 3
Divide by the original value
20 / 80 = 0.25. Dividing by anything else changes the meaning of the answer, even if the number looks reasonable.
- 4
Multiply by 100 for the percentage
0.25 x 100 = 25.00%. Check the direction: an increase from 80 to 100 must come out positive.
- 5
If the original was zero or negative, switch to absolute terms
The ratio has no useful meaning when there is no base to divide by. Report the absolute movement and describe it in words instead.
For worked examples, common mistakes and the limits of this formula, read the full How To Calculate Percentage Change page.