My campaign brought no orders: why is cost per conversion shown as undefined and not zero?
Because CPA is spend divided by conversions, and dividing by zero has no answer. If the calculator showed zero, it would read as if each order cost you nothing, when in fact you paid and got no order at all. So it shows 'Undefined' with the reason, and every other metric is still calculated.
What the calculator shows, exactly
A campaign was shown 15,000 times and got 300 clicks for a spend of 450 AED, with no orders. Here is its result in the calculator:
CTR 2%, CPC 1.5 and CPM 30: all calculated, because none of their denominators is zero.
Conversion rate 0%: this division works, zero orders out of 300 clicks.
CPA 'Undefined', with a message: conversions are zero, spend cannot be divided by zero, and it does not mean conversions are free.
Notice the difference between conversion rate and CPA. The first divides orders by clicks, so a zero on top simply gives 0%. The second divides spend by orders, so a zero underneath leaves nothing meaningful. Each metric is judged on its own, which is why one undefined metric does not blank out the rest of the report.
Why a zero here would be dangerous, not just untidy
Picture copying five campaigns into a sheet and sorting them from cheapest CPA to most expensive. If this campaign's CPA were written as zero, it would sit at the top as your best performer, when it is the only one that sold nothing. Average the CPAs of all five and the zero drags the average down and flatters the whole picture. 'Undefined' stops that mistake before it starts.
One order changes everything
Enter the same figures with one order: CPA becomes 450, the entire spend, and conversion rate 0.33%. Going from zero orders to one does not make the campaign profitable; it means everything you spent is now the cost of that single order. With counts this small, do not judge the campaign on CPA alone. Look at how much you have spent and how much of the test is left.
- Open the Campaign performance calculator and enter impressions, clicks and spend, with conversions at zero as in the report.
- Read CTR and CPC to see whether the problem is getting attention or what happens after the click.
- Press 'Copy result': the 'Undefined' message is copied with the figures, so a zero never slips into your report by mistake.
How to put it in a report or a message to your partner
The plainest wording is the clearest: we spent 450 AED, the campaign got 300 clicks, and we recorded no orders. That sentence is more honest than any CPA figure. If you want to know how much you would have needed to sell to cover the spend, go to the ROAS calculator with your sales value and margin. And before writing the campaign off, make sure the ad link carries UTM campaign link builder parameters, so no real orders went unattributed.
Common questions
Why not show infinity instead of 'Undefined'?
Infinity is not a number you can add up or compare in a report, and it can break spreadsheets. 'Undefined' with a reason is clearer to whoever reads it.
Conversion rate shows 0% rather than undefined. Is that a contradiction?
No. Conversion rate divides by clicks, which are 300, so zero is the correct answer. It shows undefined only when clicks themselves are zero.