RPM
Also called revenue per mille · revenue per thousand views · RPM rate
Revenue per mille: a channel's estimated ad revenue per 1,000 monetised views, YouTube's headline earnings-rate figure.
In more detail
RPM is reported inside YouTube Studio as an estimate that already nets out YouTube's cut and applies to monetised playback specifically, not raw views. It moves with the advertiser demand behind a niche, the audience's country, the time of year, and the video's length, which is why the same channel can see its RPM double or halve between months without anything in the content changing.
Example
A history channel with a strong US audience might see an RPM of around $3 to $6. At a $4 RPM, 100,000 monetised views works out to roughly $400. A similar channel whose audience skews toward a smaller ad market can post the same view count for a fraction of that revenue, purely on the strength of who is watching.
Why it matters
RPM is the number that decides whether a niche is worth the hours it costs, and it is easy to chase for the wrong reason. A high-RPM subject you cannot stay curious about for years is usually a worse bet than a lower-RPM one you can, because the videos that get made consistently beat the videos that pay well per view and stop after a dozen.