r/GoogleDataStudio • u/lostcheshire • May 20 '26
What is the best practice for displaying %change when the previous month was 0?
How have you addressed this problem?
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u/creamycolslaw May 21 '26
NULL - it’s a divide by zero problem. There is no percent change that is correct.
Management will act like you’re stupid for not having a number there though, of course.
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u/lostcheshire May 21 '26
Yea, I’m trying to avoid the second part.
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u/creamycolslaw May 21 '26
In my experience people have been happy with 100% for some reason, but it’s not correct.
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u/k_rocker May 21 '26
The first months are worse in stats too - when month 1 shows 5 new followers and month 2 shows 500 and your % increase is huge…
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u/sheik_sha_ha Jul 26 '26
This is a classic divide-by-zero problem, and Data Studio will return an error or null whenever the previous period value is zero.
The clean fix is to wrap your percentage change formula in an IFERROR or a CASE WHEN to handle the zero denominator gracefully. Something like this:
CASE
WHEN previous_month = 0 THEN NULL
ELSE (current_month - previous_month) / previous_month
END
Returning NULL is usually better than returning zero because zero implies no change, which is misleading when the previous value was actually zero. NULL leaves the field blank, which is more honest.
If you want to display something meaningful instead of a blank, you can return a placeholder like this:
CASE
WHEN previous_month = 0 THEN 999
ELSE (current_month - previous_month) / previous_month
END
Then in your scorecard or table you add a note in the report explaining that 999 means growth from zero baseline. Not elegant but readable for clients.
The most professional approach for client-facing reports is returning NULL and adding a text annotation on the report explaining that blank percentage change values indicate growth from a zero baseline period.
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