CPM, CPC and CTR show up in every ad dashboard. Each one measures something different: what you pay for visibility, what you pay for a visit and how well your ad earns attention. Once you see how they connect, reading a campaign report becomes much easier.
The three formulas
CPM (cost per mille) = Total cost ÷ Impressions × 1,000
CPC (cost per click) = Total cost ÷ Clicks
CTR (click-through rate) = Clicks ÷ Impressions × 100%
“Mille” is Latin for thousand, so CPM is the cost of 1,000 ad impressions. An impression is counted each time the ad is shown.
One campaign, three metrics
Suppose a campaign spends $500, is shown 125,000 times and gets 1,500 clicks.
| Metric | Calculation | Result |
|---|---|---|
| CPM | $500 ÷ 125,000 × 1,000 | $4.00 |
| CTR | 1,500 ÷ 125,000 × 100% | 1.2% |
| CPC | $500 ÷ 1,500 | $0.33 |
One campaign, three metrics: $500 spend, 125,000 impressions, 1,500 clicks.
How the metrics connect
If you know any two of CPM, CPC and CTR, you can find the third:
CPC = CPM ÷ (CTR × 1,000)
Check with the example: $4.00 ÷ (0.012 × 1,000) = $4.00 ÷ 12 = $0.33. This relationship explains why a better CTR lowers your cost per click even when the CPM stays the same.
Which metric matters for your goal?
| Goal | Main metric | Why |
|---|---|---|
| Brand awareness / reach | CPM | You pay to be seen by as many people as possible |
| Website traffic | CPC | You care about the cost of each visit |
| Ad and audience fit | CTR | Shows whether the message is relevant to the people seeing it |
| Sales or leads | Cost per conversion | Clicks only matter if they lead to results |
Mistakes to avoid
- Comparing CTRs across different platforms or ad formats. Search ads and display ads behave very differently.
- Chasing a high CTR with misleading ad copy. You will pay for clicks from people who leave straight away.
- Looking at CPM alone. Cheap impressions are worthless if the audience is wrong.
- Using too little data. A few hundred impressions can swing CTR wildly.
A note for publishers
If you run ads on your own site, the same idea appears as RPM (revenue per 1,000 impressions or pageviews). The calculation mirrors CPM but measures earnings instead of cost.
Converting between the three
CPC = CPM ÷ (1,000 × CTR)
A $12 CPM with a 1.2% click-through rate gives a CPC of 12 ÷ (1,000 × 0.012) = $1.00. Raising CTR to 1.8% at the same CPM cuts CPC to about $0.67, which is why better creative lowers your cost per customer. Follow the chain all the way to sales in customer acquisition cost (CAC) explained.
Calculate your numbers
Use the CPM calculator to find cost per thousand impressions, and the CTR calculator to work out click-through rate from your clicks and impressions.
Frequently asked questions
CPM is the cost of 1,000 impressions, so you pay for visibility. CPC is the cost of each click, so you pay for visits.
Divide CPM by CTR (as a decimal) times 1,000. With a $4 CPM and a 1.2% CTR, CPC = 4 ÷ 12 = $0.33.
Usually it means the ad is relevant, but only if those clicks turn into results. A misleading ad can have a high CTR and poor conversions.
It varies widely by platform, country, audience and season. Compare against your own past campaigns rather than a single industry figure.
Related calculators
Related articles
- Customer Acquisition Cost (CAC): Formula and Examples
- What Is a Good CTR? How to Calculate and Improve It
- How to Budget for SEO: A Simple Cost Framework
