Quick answer: Spreadsheet percentage change is straightforward when the old and new values appear in separate cells. A small error in formatting, however, can produce confusing answers.
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Understand the method
If A2 contains the original value and B2 the new value, use =IF(A2=0,"",(B2-A2)/A2) and format the output cell as a percentage.
This calculation is appropriate for ordinary positive-baseline comparisons. A zero starting value has no defined percentage change under the standard formula, so the formula returns a blank instead.
Worked example
If A2 = 1,500 and B2 = 1,800, the spreadsheet returns 20%. If B2 = 1,200, it returns −20%.
What people often get wrong
Do not both multiply by 100 in the formula and apply percentage formatting. That produces an incorrect display.
A practical way to use this
Use descriptive column headings such as “Previous month” and “Current month” so the formula’s direction stays clear.
Frequently asked question
Why does Excel show 0.2? It may be correctly storing 20% as 0.2; format the cell as Percentage.
Spreadsheet reference points matter
If the original value is in A2 and the new value is in B2, use =(B2-A2)/A2, formatted as a percentage. A calculation returning 0.25 is 25% when the cell is formatted appropriately.
Apply it to your own task
To avoid a division error when A2 is zero, use =IF(A2=0,"N/A",(B2-A2)/A2). Never silently substitute 0% for an undefined change; that conceals a real limitation in the comparison.
Related reading
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