The formulas
CPM = Spend / Impressions x 1,000
CPC = Spend / Clicks
CTR = Clicks / Impressions x 100
Conversion rate = Conversions / Clicks x 100
CPA = Spend / Conversions
CPC = Spend / Clicks
CTR = Clicks / Impressions x 100
Conversion rate = Conversions / Clicks x 100
CPA = Spend / Conversions
How the metrics connect
These numbers are a chain. CPA is simply CPC divided by conversion rate, and CPC is CPM divided by (CTR x 10). That tells you where to look when costs rise:
- High CPM - you are paying a lot to be seen. Audience is small or competitive, or it is a seasonal peak (Q4).
- Low CTR - the ad is not earning the click. Fix the hook, image or offer.
- Low conversion rate - people click but do not buy. Fix the landing page, price or trust signals.
Typical benchmarks
| Platform | Typical CPM | Typical CTR |
|---|---|---|
| Meta (Facebook/Instagram) | $8 - $20 | 0.9% - 1.5% |
| Google Search | n/a (CPC based) | 3% - 6% |
| Google Display | $2 - $6 | 0.3% - 0.6% |
| TikTok | $5 - $12 | 0.8% - 1.5% |
| $25 - $60 | 0.4% - 0.7% |
Benchmarks vary widely by country, industry and season - treat them as a rough sanity check, not a target.
Frequently asked questions
What is the difference between CPM and CPC?
CPM is the cost of 1,000 ad impressions. CPC is the cost of a single click. You can convert between them with CTR: CPC = CPM / (CTR x 10).
What is a good CPA?
Any CPA below the profit you make per conversion. Use the break-even CPA calculator to find your ceiling.
Does this work for Google Ads and Meta Ads?
Yes. The formulas are the same on every platform - just copy spend, impressions, clicks and conversions from the dashboard.