Impression Share
The percentage of total available impressions that your ads actually received in a given time period. Google Ads breaks this into two sub-metrics: impression share lost to budget (your budget ran out before all eligible auctions completed) and impression share lost to rank (your Ad Rank was too low to compete). Impression share is reported at the campaign, ad group, and keyword level. A 100% impression share means your ads appeared for every eligible search. For branded keywords, top advertisers typically target 90-95% impression share, while non-branded campaigns often operate at 40-70%.
Why It Matters
Impression share reveals how much potential reach you are leaving on the table. If your campaigns are profitable but only capturing 40% of available impressions, increasing budget could significantly scale your results. The distinction between budget-lost and rank-lost impression share guides the right optimization approach: budget-lost share requires higher daily budgets, while rank-lost share calls for Quality Score improvements or higher bids. Monitoring impression share trends against competitor activity also reveals when new entrants are stealing visibility. For high-value branded keywords, losing impression share means competitors are appearing on your own brand name searches.
Example
A Google Ads campaign shows an impression share of 55%, with 30% lost to budget and 15% lost to rank. The team first addresses the budget constraint by increasing daily spend by 50%, which captures budget-lost impressions and lifts impression share to 72%. Next, they improve ad relevance and landing page speed to boost Quality Score, recovering the rank-lost share and reaching 85% impression share overall. The result is a 52% increase in conversions at a stable CPA, demonstrating that the market has profitable demand the brand was previously missing.
Related Terms
Quality Score
A rating on a 1-10 scale used by Google Ads to measure the relevance and quality of your keywords, ads, and landing pages. It is composed of three components: expected click-through rate, ad relevance, and landing page experience, each rated above average, average, or below average. Quality Score is calculated at the keyword level and updated dynamically as performance data accumulates. While other platforms like Microsoft Ads use similar quality metrics, Google's Quality Score is the most widely referenced. A score of 7 or above is generally considered good, while scores below 5 indicate significant optimization opportunities.
CPM
Cost Per Mille (mille meaning one thousand in Latin) is the cost an advertiser pays for one thousand ad impressions. It is the standard pricing model for display, video, and programmatic advertising. CPM is calculated by dividing total ad spend by total impressions and multiplying by 1,000. Average CPMs range widely: social media display ads cost $5-$12, YouTube pre-roll averages $10-$30, and connected TV campaigns can reach $25-$50. CPM is most useful for comparing reach efficiency across channels and formats when the primary goal is brand awareness rather than direct response.