What is CPM (Cost Per Mille)?

CPM (cost per mille) is the amount an advertiser pays for one thousand ad impressions. You calculate it by dividing total ad spend by impressions delivered, then multiplying by 1,000. It is a media-cost metric, not a performance metric, so a low CPM is only good if the impressions actually convert.

What is the CPM formula?

CPM = (spend / impressions) x 1,000. If you spend $400 and earn 100,000 impressions, your CPM is $4.00. Because it isolates the cost of reach, CPM lets you compare how expensive it is to put an ad in front of people across platforms, placements, and audiences.

What influences your CPM?

Three things move CPM the most: auction competition, targeting, and creative quality. Crowded auctions (holidays, big sale windows) and narrow, high-demand audiences push the price up. Platforms also reward relevant, engaging creative with cheaper delivery, so a strong ad can lower your CPM while a weak one raises it.

Why does CPM rise over time?

A steady climb in CPM on an unchanged ad is often a symptom of creative fatigue. As your audience sees the same video too many times, engagement drops, the platform charges more to keep serving it, and your costs quietly inflate. The fix is not more budget but fresh angles and hooks tested on a regular cadence — and the fastest way to keep new creative flowing is to generate ads inside Claude: connect Polaris once, then ask in plain chat for a batch of fresh variants that render right in the conversation.

Does a low CPM mean a profitable ad?

No. CPM only measures the price of reach; it says nothing about sales. A cheap CPM paired with weak conversion still loses money, while a higher CPM on a converting ad can be very profitable. Pair CPM with downstream numbers, and use a ROAS calculator to see whether the impressions you are buying actually pay off.