Cost per purchase
Definition: Cost per purchase is ad spend divided by the number of purchases reported by an advertising platform such as Meta. It depends on which purchases the platform credited to an ad, so it differs from the cost per order counted from the shop, where spend is divided by all paid orders.
Two names, two different divisors: purchases the platform reported and orders the shop actually took.
Also called: cost per purchase, purchase CPA, cost per result (purchase)
The demo has sample data; the login comes to your e-mail.
Why it matters for a shop
Cost per purchase tells you what a purchase credited to an ad costs on average. It is easy to confuse with cost per order. When Meta reports fewer or more purchases than the shop has orders, the two costs drift apart, and neither is “wrong”: they differ by definition.
How Basketly handles it
- Campaigns: cost per purchase next to spend, purchases and purchase ROAS, with “—” at zero.
- Creatives: cost per purchase drives the fatigue rating and a creative’s momentum.
- Reports: Cost per order (total), all spend divided by paid orders, with no attribution.
Sources
What Cost per purchase does not do
- Cost per purchase ignores costs outside advertising and basket value.
- Compare it in the same window and from the same platform.
Cost per purchase divides spend by purchases the platform reported, cost per order by shop orders. The first depends on the platform’s attribution, the second does not.
When the period had no purchases the divisor is zero and the panel shows no value rather than 0.
Not with a small sample. The panel marks such values and shows spend and purchase count beside them.
See also
- ROAS (return on ad spend)The value of purchases credited to an ad divided by what was spent on that ad.Read
- MER (Marketing Efficiency Ratio)Shop revenue divided by all ad spend, with no purchases credited to particular ads.Read
- Attribution windowThe time after an ad click or view in which a platform may credit a purchase to that ad.Read
- Campaign reportingCampaigns of Meta, Google Ads, Microsoft Ads, TikTok, Pinterest and ChatGPT Ads, each platform on its own figures, next to the shop’s orders, with products in catalogue ads.Read
- ROAS, MER and cost per purchase in Meta ads: what each number measures and which to trustHow Meta's ROAS differs from MER based on shop revenue, how cost per purchase is counted, and how to read them in Campaigns and Creatives without double counting.Read
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