Learn the definition of impression share, how it works, why impression share matters in digital marketing, and the impression share formula used to measure it.

What Is Impression Share in Digital Marketing?

Impression share (IS) is a Google Ads metric that represents the percentage of impressions your ads receive out of the total number of impressions they are eligible to receive. It is known as a visibility metric for digital marketing ad performance.

Impression share is available at the campaign, ad group, keyword, and product group levels, using factors like:

• Targeting settings

• Approval status

• Ad quality

• Budget

• Rank

How Impression Share Works

Google estimates impression share by sampling ad auctions throughout the day, including auctions where your ad appeared and where it was competitive enough to appear. The sample doesn’t include Search Partner displays.

How Impression Share Works for Shopping Campaigns

For Shopping campaigns, Google assigns the impression opportunity to the highest-ranked Shopping ad from the advertiser. Only the ad’s first impression in the Search Network qualifies, and the sample excludes the Display Network and Search Partners.

What Is Absolute Top Impression Share?

Absolute top impression share (ATIS) relates to Shopping campaigns, representing the percentage of impressions shown in the most prominent position available.

What Is Performance Max Impression Share?

Performance Max (PMax) impression share measures ad visibility across Search and Shopping portions of campaigns that run across Search, Shopping, Display, YouTube, Gmail, and Maps. 

Why Is Impression Share in Digital Marketing Important?

When running digital ads, you need to be able to diagnose whether budget constraints, low bids, ad quality scores, or other factors are negatively impacting visibility. This helps you:

• Dial in ad quality

• Increase spend with optimized reach

• Maintain a competitive presence

• Improve branded search presence

What Is the Impression Share Formula?

Impression share is calculated by dividing ad impressions by your total eligible impressions:

Impression Share = Impressions ÷ Total Eligible Impressions

Related Metrics

Absolute Top Impression Share = Absolute Top Impressions ÷ Total Eligible Top Impressions

Performance Max campaigns:

Performance Max Impression Share = Impressions from Search + Shopping ÷ Total Eligible Impressions from Search + Shopping