Not Adding Up (Literally) – Google AdWords’ Glitch

Ryan Moothart May 17 2012

This is one of those short posts that will make you squint your eyes slightly, furrow your brow, tilt your head, and say, “Wait, what? This doesn’t make sense.” Like this:

I have an account in Google AdWords that has had a conversion metric calculation glitch. I first noticed it a few months ago when comparing cost/conversion and conversion rate metrics I calculated in my excel reports with the metrics reported in the AdWords interface. For this account, AdWords consistently under-reports the cost/conversion and over-reports the conversion rate. As you can guess, this has the potential to cause confusion and frustration.

Here’s a screen shot of the summary bar at the top of the data table:

adwords conversion calculation error example

The conversion types are consistent (1-per-click), but the calculations reported are incorrect. These are what they should come out to:

Cost/Conversion = $3,054.09 / 299 = $10.21

Conversion Rate = 299 / 2,190 = 13.65%

You can try calculating them yourselves right now if you’d like: Google AdWords is wrong. Now we know if they ever try to take over the world, math is their weakness.

So far, I’ve only encountered this issue with one account. Have you noticed this before in your account(s)? Let us know in the comments below.

tags : adwords error


  1. Might this be related to a click quality or courtesy credit that has been applied to your account? I know from a past experience that they don’t adjust clicks or conversion data from clicks they credit back.

  2. Another thought would be that you didn’t have conversion tracking in place for the entire period you are reporting against since they only calculated the conversion rate for the time period that conversion tracking was in place.

  3. Sam


    I’ve seen the same thing, but strangely it’s happened say one month, and never shown back up again.

  4. Thanks for the feedback, Mark. I know it’s not an issue with not having conversion tracking for a certain period of time of which I’m reporting in. And I have had cost adjusted down before to compensate for bad quality clicks in several accounts before, but the cost/conversion and conversion rates always adjusted correctly as well. I’m still doing some digging on this issue and will amend the post if I find an answer.

  5. Thanks, Sam. It’s a weird oddity that keeps recurring with just one account.

  6. Iblis


    We’ve had this too on an account. We’ve also pulled the same report twice in May for April’s data, and the number of conversions was different.

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