How is conversion rate calculated in Google Ads?

Two things follow from Google's definition. The numerator is the Conversions column, so it counts only the actions that column counts. And the denominator is eligible interactions, which Google says include ad clicks or video ad views, not a plain click count. Google does not spell out eligibility under Conv. rate itself; its description of the related cost per conversion column says any clicks that can't be tracked for conversions are removed from the calculation.

There is a second rate beside it. Google lists All conversion rate ('All conv. rate') among the columns calculated from All conversions instead of Conversions, so the two rates can differ on the same campaign in the same month.

What Riibon does with it, which is our practice and not a Google rule: where we split a cost per conversion into the price of a click and the rate at which clicks convert, we compute the rate ourselves over clicks, from the same spend, clicks and conversions, so cost per click divided by that rate gives back the cost per conversion exactly. And a rate measured on the ad click is not the whole funnel. Where a product sells after a sign-up, the share of sign-ups that buy is a separate rate, and it can move in a different month from the click rate.