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Search Impression Share

What is Search Impression Share?

Search Impression Share is the percentage of impressions won by an ad campaign or ad group or keywords, out of the total impressions the campaign is eligible for. Ad targeting, keywords, and ad scheduling all play a role in the SIS won.

Alternate names: Impression Share

How to calculate Search Impression Share

ƒ Sum(Actual Impressions) / Sum(Total Eligible Impressions)


A company’s AdWords campaign is eligible for 20,000 total impressions and gets 10,000 in one week. Therefore, the Search Impression Share for that week is 50%.

More about this metric

Search Impression Share (SIS) allows marketers to compare an ad campaign’s impressions to the total possible impressions that campaign is eligible for. Tracking this metric over time can provide a deep understanding of how successful a campaign (along with its ad groups and keywords) is in terms of reaching the largest audience possible. Essentially, SIS gives the return on opportunity cost for an ad campaign.

Impression Share eligibility is regulated by factors such as budget, keyword selection, audience targeting, region, and timing. Although it is desirable to win a large percentage of the possible Impression Share, high SIS does not necessarily result in conversions or ad clicks. Therefore, it is important to track SIS alongside Ad Clicks and conversion rate.

Additional Search Impression Share recommended resources

How impression share is calculated.How to improve your impression share.

Metrics related to Search Impression Share