Ad fill rate and eligible requests
By Theaimart ADX ·
2 minute read · AI-assisted technical review
Fill rate compares filled opportunities with eligible ad requests under a defined measurement policy. It is not the percentage of all website visits that earn revenue.
Name the event in the numerator
A fill rate needs both a numerator and a denominator. “Filled responses divided by eligible requests” measures a different boundary from “rendered impressions divided by eligible opportunities.” Agree on the event definitions before using the figure to diagnose revenue.
Do not use total visits as the denominator for an ad-request fill rate. A visit can create several opportunities or none. Retries and multiple placements can also change the count without changing the number of visitors.
Trace a synthetic funnel
Consider 10,000 eligible opportunities. Suppose 8,000 receive a usable response and 7,600 render. Response fill is 80%, while rendered-opportunity coverage is 76%. The 400-event gap deserves investigation; it should not be silently removed by calling both ratios “fill.”
If every opportunity in this model has one response, the arithmetic below is sufficient. Systems that return several ads per request need an additional explicit mapping between requests, returned ads and impressions.
javascript ·
const eligible = 10000;
const usableResponses = 8000;
const rendered = 7600;
console.log(usableResponses / eligible * 100); // 80
console.log(rendered / eligible * 100); // 76Locate the loss before changing pricing
Inspect the first boundary that loses events: request eligibility, transport, response validation, asset loading or measurement. For a renderer gap, check unsupported assets, navigation cancellation and errors before blaming buyer demand.
For a response gap, review the documented targeting and eligibility constraints and look for timeouts or malformed responses. A retry might recover an opportunity while also creating duplicate counters, so keep the attempt and opportunity identities separate.
Higher fill alone is not the objective
With 10,000 opportunities, 80% fill at a hypothetical $2 gross eCPM yields $16 gross. At 100% fill and $1 gross eCPM, the same simplified model yields $10. More filled opportunities do not necessarily mean more revenue.
Neither scenario is an ADX result. Use finalized, consistently defined reporting to assess real outcomes, and evaluate user experience alongside revenue. The linked calculator can explore assumptions, but it cannot establish available demand or payable earnings.