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Price inventory against viewable impressions only

This job converts a served-CPM rate card into a viewable CPM (vCPM) and a served-impression booking volume, so the buyer pays only for impressions that met the viewability standard. It feeds the insertion order line item and the billing model negotiated with the publisher.

What you need first

  • Served CPM from the publisher or SSP rate card for the exact placement and format
  • Viewability rate for that placement from the verification vendor's trailing report (IAS, DoubleVerify, or MOAT), filtered to device and creative size
  • MRC viewability threshold applied by the vendor (50% of pixels, 1 continuous second for display, 2 seconds for video)
  • Line budget or impression goal from the media plan
  • Buyer's vCPM ceiling or market benchmark for the format, if one exists

The procedure

  1. Pull the served CPM from the rate card for the exact placement and format being booked
  2. Pull the viewability rate for that placement from the verification vendor's trailing report, filtered to device and creative size
  3. Calculate vCPM by dividing served CPM by the viewability rate
  4. Compare the vCPM against the buyer's vCPM ceiling or the market benchmark for that format
  5. Convert the budget into a viewable impression target by dividing budget by vCPM
  6. Back into the served impression volume to book by dividing the viewable impression target by the viewability rate
  7. Confirm with the publisher which billing model applies: vCPM billing where they absorb non-viewable risk, or served CPM billing with a viewability make-good clause

Worked through with numbers

Rate card served CPM is €8.00 for desktop in-content display. IAS trailing 90-day viewability for this placement is 72%. vCPM = 8.00 / 0.72 = €11.11. Line budget is €50,000. Viewable impressions purchasable at vCPM billing = 50,000 / 11.11 × 1000 = 4,500,450, call it 4.5M viewable impressions. If the publisher bills on served CPM instead, served impressions to book = 4.5M / 0.72 = 6.25M. Check: 6.25M served × €8.00/1000 = €50,000, which matches the budget. Read it as: at 72% viewability the buyer needs to book 6.25M served impressions to guarantee 4.5M viewable ones, and the effective price for what actually counts is €11.11 vCPM, not the €8.00 on the card.

Where it goes wrong

  • Use the viewability rate for the specific placement, device, and creative size being booked, not an account-level or blended average, since mobile and desktop rates can differ by 20 points or more
  • Separate vCPM billing from served-CPM-with-guarantee before quoting a number, since the two put viewability risk on different sides and produce different effective prices for the same served CPM
  • Match the vendor's measurement window to the format before comparing rates, since a 1-second display standard and a 2-second video standard are not interchangeable inputs to the same formula
  • Pull a fresh viewability rate for the current creative and flight, not a rate carried over from a prior campaign, since creative size and page position change viewability materially

How to know it is right

Multiply the calculated vCPM by the viewability rate and confirm it reproduces the original served CPM from the rate card before sending the line item forward.

Terms used

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