<b>A $6 CPM and a $24 RPM describe the same ad slot. Stop comparing them.</b>

<b>A $6 CPM and a $24 RPM describe the same ad slot. Stop comparing them.</b>

CPM = paid per 1,000 impressions of one unit. RPM = earned per 1,000 pageviews across all units. RPM = (CPM × ads/page × fill × viewable rate) blended.

Worked example, illustrative:
— 4 units/page, avg CPM $6
— Fill 92%, viewable 71%
— Raw 4×$6 = $24/1k impr
— After fill+view: $24 × .92 × .71 ≈ $15.7 page RPM

The leakage (fill, viewability) eats a third before you see it.

So what: never set a goal in CPM. Buyers control CPM; you control the multipliers. ▼ -34% slippage CPM→RPM.