ScaleySearch Impression Share: The Formula and What It Means
The formula Google uses, the lost impression share columns that tell you why you missed out, and when chasing a higher share is a waste.
Written and reviewed by Christopher Krassnig
Published Last checked
Impression share is the percentage of impressions your ads got out of all the impressions they were eligible for. The formula is impressions divided by total eligible impressions. A 60% search impression share means your ads showed in 60 of every 100 searches they could have. Google updates it within 1 to 2 days.
Also called: search impression share, IS, absolute top impression share
The Impression Share Formula
Google writes it as: impression share = impressions / total eligible impressions.
"Eligible" is the key word. Google estimates it "using many factors, including targeting settings, approval statuses, and quality." It counts auctions where your ad showed and auctions where it was competitive enough to show. Google's example: it could include auctions where your ad would show at twice its bid, but leave out ones where it would need a 1,000% bid increase.
You can see it for campaigns, ad groups, product groups (Shopping) and keywords. It is an estimate, so Google says small swings do not always mean you need to act.
The Columns to Add, and What Each One Tells You
Add these from the Competitive metrics menu. Google's own definitions:
| Column | What it measures |
|---|---|
| Search impr. share | Impressions on the Search Network divided by the estimated impressions you were eligible for. |
| Search lost IS (budget) | How often your ads did not show on Search because the budget ran out. Campaign level only. |
| Search lost IS (rank) | How often your ads did not show on Search because of poor Ad Rank. |
| Search exact match IS | Impression share on searches that matched your keywords exactly or were close variants. Not for Shopping. |
| Absolute top impression share | For Shopping, the share of impressions in the most prominent position. |
| Display impr. share | Impressions on the Display Network divided by the estimated impressions you were eligible for. |
Read the two lost columns first. Lost to budget means you ran out of money, so the fix is budget or narrower targeting. Lost to rank means you lost the auction, so the fix is a better bid, a better ad or a better landing page. Raising budget does nothing for rank.
Impression Share for Shopping and Performance Max
Shopping counts it a little differently. Several of your products can show in one auction, so Google gives the impression opportunity to your highest-ranked Shopping ad only. Later impressions in that same auction do not count toward impression share. Shopping impression share comes from Search Network traffic only.
For Performance Max, Google uses Search and Shopping together: impressions from Search + Shopping / total eligible impressions from Search + Shopping. See what Performance Max is.
When a Higher Impression Share Is Worth It
100% is not the goal. Every extra point costs more than the last, because you are buying the auctions you used to lose.
Chase it on searches that already make money, like your brand name and your best products. If those lose share to budget, you are turning away buyers. Leave it alone on broad or unproven searches, where a low share keeps a test cheap. Google also offers a Target impression share bid strategy, but it bids for visibility, not sales, so most stores use it only for brand searches.
Example: A Watch Store Reads Its Brand Campaign
Made-up numbers, to show the method. A watch store's brand campaign shows: Search impr. share 70%, Search lost IS (budget) 25%, Search lost IS (rank) 5%.
So in about 25 of every 100 brand searches, the ad did not show because the daily budget ran out. Those are people typing the store's own name.
The store raises the brand budget and checks again after a week. Lost to budget falls toward zero. The rank number stays small, so it leaves bids alone. Its budget calculator run tells it what the extra searches should cost first.
Common Mistakes
Raising budget to fix lost IS (rank)
Lost to rank means you lost the auction. More budget does not help. Better bids, ads or landing pages do.
Chasing 100% everywhere
The last points cost the most. Buy share on searches that already sell, not on tests.
Adding up impression share across the account
Google reports it separately per campaign type and does not add it up across the account.
Reacting to small daily swings
It is an estimate. Google says small changes do not always need action.
Questions People Ask
Divide the impressions your ads got by the total impressions they were eligible to get. Google estimates the eligible number from targeting, approval status and quality.
Google's Own Pages We Quoted
Every rule, limit and size on this page comes from these pages, read on 8 October 2026. Google changes them, so check the page itself before you act.
Where to Go Next
- Google Ads Budget CalculatorWhat the searches you are missing would cost.
- What Is Quality Score?Quality is part of Ad Rank, and Ad Rank drives lost IS (rank).
- Google Ads Optimization Checklist12 checks in order, impression share included.
- Google Ads Auction Insights: Every Metric and What to Do NextSee who took the impression share you lost.
Ask Where Your Ad Money Went
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