CPM vs. RPM on YouTube
CPM is what advertisers pay per thousand ad views; RPM is what you actually earn per thousand video views.
What it means
CPM (cost per mille) is the rate advertisers pay per thousand monetized ad impressions. RPM (revenue per mille) is a different number entirely — your actual total revenue, from ads and beyond, divided by total views. RPM is always the smaller, more honest number.
Why it matters
Creators often see a high CPM being reported somewhere and assume that is their earning rate — it is not. RPM accounts for YouTube's cut and for views that were never monetized at all, so it is the number that reflects what actually lands in your account.
ask datanephew
Which number should I actually pay attention to?
RPM — it reflects your real revenue per thousand views. CPM only describes the ad market, not your take-home.
Why did my RPM drop even though CPM looks stable?
Ask datanephew to check whether a larger share of recent views went unmonetized, or whether view counts grew faster than ad revenue — either can pull RPM down even when CPM holds steady.