How Impression Share Is Calculated
Impression Share = Your Impressions / Total Eligible Impressions. Eligible impressions are estimated based on your targeting settings, keywords, bid, Quality Score, and auction competition. Google Ads breaks lost impression share into two categories: lost due to budget (your daily budget ran out) and lost due to rank (your Ad Rank was too low). For example, 60% impression share with 25% lost to budget and 15% lost to rank tells you exactly where to focus optimization efforts.