{
  "slug": "paid-cost-per-conversion",
  "name": "Cost per conversion",
  "aliases": [
    "CPA",
    "Cost per acquisition"
  ],
  "definition": "What one ad-platform conversion cost on average, total ad cost divided by the ad platform's conversion count.",
  "category": "Paid search",
  "type": "monetary",
  "unit": "account currency per conversion",
  "direction": "lower-better",
  "verification": "verified",
  "calculation": "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",
  "aggregation": "A ratio of two sums, recomputed at the queried grain, never averaged across breakdown rows.",
  "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"
  ],
  "requiredFilters": [
    "date_range"
  ],
  "sources": [
    "google-ads"
  ],
  "reports": [
    "paid-search-performance-report"
  ],
  "skills": [
    "paid-efficiency-review",
    "paid-organic-balance",
    "search-to-revenue"
  ],
  "verbs": [
    "paid_search_overview"
  ],
  "rungs": [
    "R5"
  ],
  "levers": [
    "L8"
  ],
  "questions": [
    "What is our cost per conversion by campaign?",
    "Which ad groups are the least efficient?"
  ],
  "interpretation": "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": [
    "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.",
  "failureModes": [
    "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)."
  ],
  "notSameAs": [
    {
      "slug": "conversion-rate",
      "why": "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."
    },
    {
      "slug": "paid-ad-cost",
      "why": "Cost is the absolute amount spent; cost per conversion is that amount divided by the ad platform's own conversion count.",
      "mirroredFrom": "paid-ad-cost"
    },
    {
      "slug": "paid-average-cpc",
      "why": "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.",
      "mirroredFrom": "paid-average-cpc"
    }
  ],
  "related": [
    "paid-ad-cost",
    "paid-conversions",
    "paid-average-cpc"
  ],
  "workflows": [],
  "lastVerified": "2026-08-04"
}