How CPM actually works
CPM prices attention by the thousand. Divide your cost by impressions delivered and multiply by a thousand, and you have the rate you paid to reach an audience. On Meta, TikTok, YouTube, and programmatic display, CPM is the underlying auction currency even when you optimise toward clicks or conversions, because the platform is really selling impressions and inferring who is worth showing your ad to. A low CPM is not automatically good: reaching a thousand of the wrong people cheaply is worse than reaching a thousand of the right people at a premium.
Why CPMs rise and fall
CPM is set by demand for the audience you want. It climbs when more advertisers compete for the same people, which is why CPMs spike in Q4 around Black Friday and the holidays, and why narrow, high-value audiences cost more than broad ones. Ad quality matters too: platforms reward creative that holds attention with cheaper delivery, so a fatigued ad quietly raises your CPM as the algorithm has to work harder to place it. Seasonality and creative freshness move CPM as much as your targeting does.
How CPM, CPC, and CTR connect
These three metrics are bound by one identity: your effective CPC equals your CPM divided by clicks per thousand impressions, which is just CPM over CTR times ten. That means you can lower cost per click two ways: pay a lower CPM, or earn a higher CTR from the same impressions. In practice, improving CTR with better creative and targeting is usually the more durable lever, because it also signals quality to the platform and can pull your CPM down at the same time.
When buying on CPM makes sense
CPM buying suits goals where being seen is the point: brand launches, reach campaigns, and top-of-funnel prospecting where you are building an audience to retarget later. It is the wrong lens for bottom-of-funnel search intent, where paying per click or per conversion aligns cost with response. iClick reads CPM as a cost-of-attention input, then judges the campaign on what that attention produced downstream, never on the CPM in isolation.
