What is impression share?
Impression share is the percentage of impressions your ads received out of the total they were eligible to get. An 80% impression share means you showed for four of every five available chances.
It reframes performance as opportunity. A campaign can look busy in raw impressions while still missing most of the demand it could have reached.
The formula.
Impression share = (impressions received ÷ total eligible impressions) × 100. The ad platform estimates the eligible total from auctions you qualified for.
The same reporting also splits the share you lost into two causes, budget and rank, which is the most useful part for deciding what to fix.
A worked example.
Your ads receive 8,000 impressions out of 10,000 eligible. Impression share is 8,000 ÷ 10,000 × 100, which is 80%.
What is a good impression share?
80% and up is strong coverage for a priority campaign. Between 50 and 80% leaves clear room to grow, and below 50% means you are missing most of your eligible impressions. Before adding budget, check whether you are losing share to budget or to rank, because the fix is different for each.
Winning more impressions only pays if those extra impressions turn into customers. Reading impression share against the demand you have not captured yet keeps the focus on growth, not just visibility.
How to improve it.
If you are losing share to budget, raise or reallocate spend. If you are losing it to rank, improve your bid or Quality Score so more auctions are winnable. The platform tells you which lever applies.
The impressions you do not have to buy come from ranking organically, which is how you compound visibility instead of renting it through a channel that does not bill per click.