Percentage Change in Excel: Increase, Decrease, and a Zero Starting Value
A percentage-change column can look reasonable while using the wrong denominator. It can also hide undefined comparisons when a formula replaces every error with zero. Decide what the original value represents before formatting the result.
Keep the old and new values in a fixed order
Use Excel desktop with numeric values in B2:C6 and the sample headers in row 1. Put absolute_change in D1 and relative_change in E1. The word old means the reference period; it is the denominator for the positive-baseline calculation.
Check units and periods before calculating. Comparing a monthly amount with a quarterly total can produce a mathematically correct but meaningless percentage. The fixture describes abstract measurements and does not prescribe a financial reporting convention.
Calculate the change before formatting it
Enter =C2-B2 in D2 and =(C2-B2)/B2 in E2 for the first row. E2 is the decimal 0.25; Percentage format displays 25%. Do not multiply by 100 and then apply Percentage format, or the same underlying growth will display as 2500%.
For row B the denominator is 100, producing -20%. This is why an increase from 80 to 100 and a decrease from 100 to 80 have different percentages even though the absolute difference has the same magnitude.
Flag baselines outside the declared rule
Use the guarded formula below for the full fixture and fill through row 6. It treats a nonpositive baseline as Review baseline. A missing input produces Missing input rather than allowing an empty cell to behave like zero.
The formula assumes nonblank inputs are numeric. Check =ISNUMBER(B2) and =ISNUMBER(C2) if your import contains numeric-looking text. Do not hide all input errors with IFERROR(...,0): zero growth is a valid result with a different meaning.
=IF(OR(B2="",C2=""),"Missing input",IF(B2<=0,"Review baseline",(C2-B2)/B2))Keep a useful result for zero and negative baselines
Moving from zero to 20 has an absolute increase of 20, but division by the original zero is undefined. Retain that absolute change and a clear flag. A text label such as New can be useful if your report explicitly defines it; it should not be a numeric growth rate.
A negative reference can reverse the apparent sign of relative change. For -20 to 10, the ordinary quotient is -150%, despite the numeric value increasing. This guide therefore requires a separate agreed rule instead of silently using ABS(old) as a universal correction.
Distinguish percentage points from relative change
In H2 enter 20% and in I2 enter 25%. =I2-H2 returns 0.05; displayed as Percentage it is 5%, representing a difference of 5 percentage points. =(I2-H2)/H2 returns 25%, the relative increase from the original rate.
Label these columns Percentage-point change and Relative change so readers know what was measured. Do not sum row-level percentage changes to obtain an overall growth rate; when meaningful, calculate growth from comparable aggregated old and new totals.
Check the result and preserve precision
The expected output retains decimal fractions 0.25, -0.2 and -1 so an importer can choose its own percentage display. Compare the flag rows separately instead of averaging text labels together with numbers.
Keep full numeric precision for later calculations and round the display only as needed. Verify the same baseline policy with the report owner before publishing an operational dashboard. The sample proves the stated arithmetic, not the suitability of a percentage convention for every metric.
Common questions
What is the denominator?
For positive-baseline change, divide new minus old by old.
Should a zero baseline show 0%?
No. The relative change is undefined; keep an explicit flag and the absolute change.
Why does 20% to 25% mean 25% growth?
The increase of 0.05 divided by the original 0.20 is 0.25. The difference is also 5 percentage points.
Sources & method
Examples and diagrams use synthetic data. Application instructions follow the linked documentation; available menus and options can vary. Our sample checks do not establish behavior in every Excel or Google Sheets version. Read our AI-assisted editorial method.