Formula
Max CPC = sales per order × conversion rate × target ACoS
Use conversion rate and ACoS as decimals.
Worked example
For a $40 sale, a 10% conversion rate and a 30% target ACoS, max CPC is $40 × 0.10 × 0.30 = $1.20. Ten clicks cost $12 and, at the assumed rate, produce one $40 order. The resulting ACoS is 30%.
At a 5% conversion rate, the same target supports only $0.60 per click. At 20%, it supports $2.40. These are arithmetic scenarios with unchanged order value and target, not predictions that buying more clicks will produce a fixed number of orders. Small samples can make the conversion assumption especially uncertain.
Why it matters for profit
A click ceiling turns your product target into a bidding reference. Use actual sales per order when it differs from the single-unit price, and check whether the products represented by those sales have similar margins. At break-even ACoS, the ceiling retains no contribution after ads under the model.
The platform’s bid field and your observed average CPC are different quantities. Placement boosts and dynamic bidding can increase the bid eligible for an auction. Review the combined settings before copying a calculated click value into a keyword bid, and revisit it when conversion rate, price or product costs change.