Impression share (IS)
Impression share is the percentage of impressions an ad received out of the total it was estimated to be eligible for. In Google Ads, Search impression share shows how often ads appeared when they could have, and lost impression share splits the shortfall between budget and Ad Rank.
How is impression share calculated?
Google's formula is impressions divided by total eligible impressions. Eligibility is estimated from targeting settings, approval status and quality, and covers auctions where the ad was competitive enough to show. The metrics update within one to two days, are reported separately for each campaign type and are available for the Search Network from October 2012.
What do the related metrics mean?
- Search lost IS (budget): the percentage of time ads did not show because the budget ran out, reported at campaign level only
- Search lost IS (rank): the percentage of time ads did not show because Ad Rank was too low
- Search top IS: the share of eligible impressions received among the top ads
- Search absolute top IS: the share received in the very first ad position
- Search exact match IS: impression share for searches that exactly matched the keywords or were close variants
How to act on it
Lost share to budget calls for a bigger budget, fewer keywords or tighter targeting. Lost share to rank calls for better ads and landing pages, or higher bids. A 100% impression share is rarely the right goal, because the last impressions in a market are usually the most expensive to win and the least likely to convert.
Example
A conveyancing firm's main Search campaign has a 58% impression share, with 34% lost to budget and 8% lost to rank. Most of the missing visibility is a budget decision rather than a quality problem. If its cost per lead is within target, raising the budget is the first test, not rewriting the ads.
Related terms
Further reading
Our Pay Per Click service puts this into practice for brands in the UK and US.
