What each one means
| Metric | Formula | Answers |
|---|---|---|
| CPM | spend ÷ impressions × 1,000 | How much does reach cost? |
| CTR | clicks ÷ impressions × 100 | Does the ad earn clicks? |
| CPC | spend ÷ clicks | How much does a click cost? |
| CPA | spend ÷ conversions | How much does a result cost? |
| CPV | spend ÷ video views | How much does a view cost? |
How CTR links CPM and CPC
CPC = CPM ÷ (CTR% × 10)
A 10 CPM with a 1% CTR gives a 1.00 CPC. Double the CTR to 2% and CPC halves to 0.50, at the same CPM. That is why CTR is the lever most advertisers work on.
CPM or CPC: which is better?
Pay per impression (CPM) when your goal is awareness or when you expect a high CTR. Pay per click (CPC) when you only care about traffic and want to avoid paying for ads people ignore. Most platforms optimise automatically, so the bigger choice is your campaign objective.
Where CPA fits
CPA is the metric closest to profit. A low CPM or CPC means nothing if clicks don't convert, so judge campaigns on CPA or ROAS first and use CPM, CTR and CPC to find out why.
YouTube CPM vs RPM
For creators, CPM is what advertisers pay and RPM is what you earn per 1,000 views after YouTube's share. Estimate both with the YouTube CPM calculator.
Calculators
Frequently asked questions
Is CTR a cost metric?
No. CTR is a rate. It affects your costs but is not a cost itself.
Which metric should I report to a client?
Lead with CPA or ROAS, then use CPM, CTR and CPC to explain what drove them.