Cost per conversion
also called CPACost per acquisition
Definition
What one ad-platform conversion cost on average, total ad cost divided by the ad platform's conversion count.
How it's calculated
Total ad cost divided by the ad-platform conversion count, with a null guard on the denominator so a zero-conversion period returns no rate rather than an error: `cost / NULLIF(conversions, 0)`.
- Numerator
- Total ad cost over the period
- Denominator
- Ad-platform conversions over the period
Scope, grain and dimensions
- Grain
- One number per date range, or one row per group_by value.
- Dimensions
- keyword · campaign_keyword · page · adgroup_name · campaign_name · campaign_type · intent · category · country · device
- Required filters
- date_range
- Aggregation
- A ratio of two sums, recomputed at the queried grain, never averaged across breakdown rows.
- Metric type
- monetary · account currency per conversion
Data sources
Where you'll see this
Named reports that normally include this metric.
Paid search performance report
Skills and analyses that use it
Skills carry the judgment; the analysis verbs do the reading.
Analysis verbs
paid_search_overview
Method rungs and levers
A rung tells you what a movement here can and cannot explain, read the rungs below it first.
levers L8 Paid/organic interplay
Ask Quattr
- "What is our cost per conversion by campaign?" Simulate this →
- "Which ad groups are the least efficient?" Simulate this →
How to read it
The price of an outcome, in the ad platform's own attribution. It is the paid efficiency number executives recognise, and it is only comparable across campaigns that count the same conversion actions. A rising cost per conversion with flat cost per click means the click quality changed, not the auction price.
Caveats, freshness and failure modes
The conversions in the denominator are the ad platform's attributed conversions, not the analytics named goals. The two lenses are named whenever both appear and are never blended.
Conversion rate for paid is read from the analytics source rather than derived as conversions over clicks, dividing one system's numerator by another's denominator produces a number that is wrong in a way nobody can see.
Whole-domain only; a segment argument is ignored.
This is the one cost-family metric whose direction both direction modules agree on.
- Freshness
- ~1 day behind, Ads reporting settles overnight; same-day spend is provisional.
Common failure modes
- Comparing cost per conversion across campaigns that count different conversion actions.
- Reading a zero as good performance when it is really a null denominator (no conversions recorded).
Not the same as
The confusions that cause the most wrong decisions.
Cost per conversion Conversion rate Compare definitions →
Cost per conversion is a price from the ad platform's attribution; conversion rate is a rate measured in the analytics source against your own named goals. They come from different systems and are never combined.
Cost per conversion Ad cost Compare definitions →
Cost is the absolute amount spent; cost per conversion is that amount divided by the ad platform's own conversion count.
Cost per conversion Average cost per click Compare definitions →
CPC prices a click; cost per conversion prices an outcome. A campaign can have a cheap CPC and an expensive cost per conversion at the same time.
Watch this metric read in a real run
All runs →
Related metrics and workflows
Verification
A definition is the smallest part of this.
The measurement matters because something acts on it. Here is the rest of the showcase, in the order most people find useful.