CPM

CPM (cost per mille) is the amount an advertiser pays for an ad to be shown 1,000 times. “Mille” is Latin for one thousand.

What is CPM?

CPM is both a reporting metric and a way of buying ads. As a metric, it tells you how much you are paying per 1,000 impressions, even if you chose to pay per click. As a buying method, it means you are charged every time the ad appears, whether or not anyone clicks.

Each platform has its own variants. TikTok offers CPM for the Reach objective and oCPM (optimized CPM) for conversion, app install and lead generation objectives: you are still charged per impression, but the system picks people who are more likely to act (TikTok, Available bidding methods, August 2025). Google Display uses vCPM (viewable CPM), which charges only for impressions that can actually be seen (Google Ads Help). Under the Media Rating Council standard, a display ad counts as viewable when at least 50% of its pixels are on screen for 1 continuous second. For video, the threshold is 2 seconds (MRC, August 2015).

CPM formula

CPM = Cost / Impressions × 1,000

Meta’s own example: spend $50, get 10,000 impressions, and your CPM is $5 (Meta Business Help Center). In Vietnamese dong: spend VND 3 million for 120,000 impressions and the CPM is 3,000,000 / 120,000 × 1,000 = VND 25,000.

Flip the formula for planning: Impressions = Budget / CPM × 1,000. A VND 10 million budget at a VND 25,000 CPM buys about 400,000 impressions.

How does CPM relate to CPC and CPA?

The three metrics are linked through CTR and conversion rate (CVR):

• CPC = CPM / (CTR × 1,000). With a VND 25,000 CPM and a 1% CTR, CPC = 25,000 / 10 = VND 2,500.
• CPA = CPC / CVR. With a VND 2,500 CPC and a 2% CVR, CPA = VND 125,000.

The math shows why a cheap CPM is not automatically a good one. A VND 15,000 CPM with a CTR of only 0.4% gives a CPC of VND 3,750, more expensive than the case above.

CPM vs CPC vs CPA

On Meta and TikTok, most conversion campaigns are still billed per impression. There, CPA is a metric you set as a target (with Cost cap, for example), not the way you are billed.

Why does CPM go up and down?

• Auction competition: during the 11.11 and 12.12 shopping sales and Tet (Lunar New Year), many brands advertise at the same time, so prices climb.
• An audience that is too narrow: with fewer people to choose from, each impression costs more.
• Ad quality: platforms favor ads they predict will get engagement, so weak creative pushes CPM up.

Hypothetical example in Vietnam

A cosmetics shop runs two ad groups on TikTok for 7 days, with VND 5 million each. Group A: CPM VND 18,000, CTR 0.6%, CVR 1.5%. Group B: CPM VND 30,000, CTR 1.5%, CVR 2%. Worked through, group A’s CPA comes to about VND 200,000 and group B’s to about VND 100,000. The group with the more expensive CPM delivered orders at half the cost. The next step is to compare those numbers with the break-even ROAS for each product.

Frequently asked questions

What is a reasonable CPM?

There is no universal number. CPM varies by industry, audience, season and ad format. A more reliable benchmark is your own account’s CPM, tracked month by month within the same campaign type.

What is the difference between CPM and eCPM?

eCPM (effective CPM) is CPM calculated from actual spend, used to compare campaigns bought on different pricing models. Publishers also use eCPM to calculate revenue per 1,000 impressions.

If you want to review the CPM, CTR and CPA of your active ad accounts to find where the money is leaking, Adtek’s ads team can go through them with you. Start from our contact page.