Short answer
CPM is spend ÷ impressions × 1,000. CPC is spend ÷ clicks. CTR is clicks ÷ impressions. Conversion rate is conversions ÷ clicks, and CPA is spend ÷ conversions. They chain together: CPA = CPM ÷ (1,000 × CTR × conversion rate). In B2B, add two more: viewable CPM, which prices only seen impressions, and cost per engaged account, which shows whether the spend reached companies you want.
The formulas
| Metric | Formula | Tells you |
|---|---|---|
| CPM | Spend ÷ impressions × 1,000 | Price of attention |
| CTR | Clicks ÷ impressions | Whether the ad earns a click |
| CPC | Spend ÷ clicks, or CPM ÷ (1,000 × CTR) | Price of a visit |
| Conversion rate | Conversions ÷ clicks | Whether the page converts |
| CPA | Spend ÷ conversions, or CPC ÷ conversion rate | Price of an outcome |
| vCPM | Spend ÷ viewable impressions × 1,000, or CPM ÷ viewable rate | Price of impressions that could be seen |
| Cost per engaged account | Spend ÷ target accounts that met your engagement rule | Price of account progress |
A worked example
| Input (fictional LinkedIn campaign) | Value | Result | Value |
|---|---|---|---|
| Spend | $4,200 | CPM | $11.05 |
| Impressions | 380,000 | CTR | 0.40% |
| Clicks | 1,520 | CPC | $2.76 |
| Demo requests | 38 | Conversion rate · CPA | 2.50% · $110.53 |
| Target accounts engaged | 42 | Cost per engaged account | $100 |
Run your own numbers in the CPM, CPC, CTR and CPA calculator; it also forecasts from a budget.
How the metrics chain
CPA = CPM ÷ (1,000 × CTR × conversion rate). Halve the CTR and CPA doubles; halve the conversion rate and it doubles again. That's why a cheap CPM rarely rescues a weak ad or page, and why the CPC vs CPM calculator starts from CTR.
Three mistakes that distort comparisons
- Different click definitions. Some platforms count every click on the ad, others only clicks to your site. Compare like with like.
- CPM without viewability. A $6 CPM at 40% viewable costs $15 per thousand seen impressions. Viewability for B2B display.
- CPA without account fit. Forty cheap leads from students cost more than eight from target accounts.
Questions
How do you calculate CPM?
Spend divided by impressions, multiplied by 1,000. $4,200 for 380,000 impressions is $11.05.
What is the relationship between CPM, CTR and CPC?
CPC = CPM ÷ (1,000 × CTR). A $40 CPM at a 0.5% CTR is an $8 CPC.
Is CPA the same as cost per lead?
Only when the conversion is a lead. CPA is cost per whatever action you count: lead, demo, trial or sale.
Which metric should B2B teams lead with?
Cost per engaged target account and pipeline per $1,000. Media metrics explain why those numbers move.
Facts checked against the sources below on 19 October 2026. Ad platforms change quickly: if something here no longer matches what you see, tell us and we will update it.
