The percentage of impressions your ads actually got out of the total they were eligible to get. Google also reports why you missed the rest: lost impression share due to budget, and lost impression share due to Ad Rank.
Formula
Impression share = impressions ÷ estimated eligible impressions. Impression share + lost IS (budget) + lost IS (rank) ≈ 100%
Example
Meera's Search campaign got 80,000 impressions with an impression share of 40%, so it was eligible for about 2,00,000. Lost IS (budget) was 45% and lost IS (rank) was 15%.
How you'll hear it
“We're only at 40% impression share, and most of the loss is budget, not rank.”
What it helps you decide
Whether to raise budget, raise bids or improve ads and landing pages. Lost to budget points to budget or narrower targeting; lost to rank points to bids or ad quality.
Where people misread it
Reading a low impression share as 'raise the bids'. If the loss is mostly budget, higher bids make each click dearer and the budget runs out sooner. Also, 100% impression share is rarely worth paying for.
The story
Meera's Search campaign shows a 40% impression share. Her agency suggests raising the maximum CPC bid. She checks the two lost-share columns first.
| Impressions received | 80,000 |
| Impression share | 40% |
| Estimated eligible impressions | 2,00,000 |
|---|---|
| Missed due to budget (45%) | 90,000 |
| Missed due to rank (15%) | 30,000 |
| Extra clicks if budget loss recovered, at 5% CTR | 4,500 |
| Extra spend needed at ₹10 CPC | +₹45,000 |
What looks right: a low share suggests she is being outbid, so higher bids feel like the fix.
What it hides: three times as many impressions were lost to budget as to rank. Raising bids would spend the same ₹40,000 faster and could lower her share further.
What to look at instead: the split between lost to budget and lost to rank. Here the real choice is whether those 4,500 extra clicks are worth about ₹45,000, or whether to narrow keywords and hours so the current budget lasts.
All figures for Meera's store are fictional and for illustration only.
See where your missed impressions went
The example's numbers are filled in. Replace them with yours.
Budget is the bigger limit. Raising bids alone will not help; decide whether the extra clicks are worth the extra spend, or narrow targeting.
Don't confuse it with
- Reach: number of people who saw the ad; impression share is about how many eligible auctions you showed up in.
- Quality Score: one input into Ad Rank, which drives lost IS (rank).
Related terms
Want to use this at work? AI-led PPC Excellence is aFactor's 16-week program for paid ads.
Sources
- About impression share, Google Ads Help
- Get impression share data, Google Ads Help