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Performance & Measurement
3 min read
Impression share is the percentage of the total available impressions your ads actually won, out of all the times they were eligible to show. It tells you how much of the reachable market you are capturing — and, just as usefully, how much you are leaving on the table.
Estimate eligibility. The platform models how often you could have shown.
Count actual impressions. It tallies how often you did show.
Divide. Your impressions over eligible impressions is the share.
Diagnose the gap. Lost share is split between budget and rank reasons.
Coverage. How much of the demand you are actually reaching.
Lost to budget. Impressions missed because spend ran out.
Lost to rank. Impressions missed because bids or quality were too low.
Headroom. How much growth is still available in a market.
Growth ceiling. It shows whether you can scale or are already maxed out.
Diagnosis. It separates a budget problem from a competitiveness problem.
Competitive read. It hints at how strongly rivals are bidding.
Estimates, not truth. Eligible impressions are modelled, not counted.
Chasing 100%. Full share is rarely the efficient goal.
Context needed. High share of a tiny market means little.
Quality still rules. Share without conversions is vanity.
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