Reference library · Inventory pricing
Viewable CPM (vCPM)
Viewable CPM (vCPM) is the cost per thousand impressions that actually met a viewability standard, not the cost per thousand impressions served. It is calculated by dividing media cost by viewable impressions instead of served impressions, so vCPM is always equal to or higher than standard CPM. A buyer uses it to price and compare inventory on what was actually seen, since served impressions include ad calls that loaded below the fold, in background tabs, or off-screen.
Formula
Worked example
A display campaign serves 5,000,000 impressions for €40,000, giving a standard CPM of €8.00. The placement's measured viewability rate is 62%, so viewable impressions = 5,000,000 x 0.62 = 3,100,000. vCPM = (€40,000 / 3,100,000) x 1000 = €12.90. The planner is really paying €12.90 per thousand impressions that were viewable, 61% more than the served CPM suggested.
How it is used
Planners use vCPM to compare placements or publishers on a like-for-like basis when viewability rates differ, and to set floors in RFPs (e.g. "must deliver 70% viewability or better") rather than accepting raw served volume. Viewability itself is measured against the MRC standard: 50% of pixels in view for 1 continuous second for display, 2 seconds for video. The recurring mistake is comparing vCPM figures from different measurement vendors as if they were the same currency, when each vendor's detection methodology and viewability threshold can shift the reported rate by several points.
The common mistake
Don't compare vCPM numbers across measurement vendors without confirming they use the same viewability standard and threshold, since the underlying viewable-impression counts are not interchangeable.