Impression Share
Quick definition
Impression share is the percentage of impressions your ads received compared with the estimated number of impressions they were eligible to receive, as reported by Google Ads.
Formula
Impression Share = Impressions Received ÷ Estimated Eligible Impressions × 100
Formula variables
- Impressions Received
- The impressions your ads actually received.
- Estimated Eligible Impressions
- Google Ads estimates the number of impressions your ads were eligible to receive.
Worked example
- Impressions received
- 4,000
- Estimated eligible impressions (platform estimate)
- 5,000
4,000 ÷ 5,000 × 100
Result: 80%
The ads received 80% of the impressions Google Ads estimated they were eligible for. You read the percentage in Google Ads; the underlying figures here are illustrative.
How to interpret it
Impression share shows how much of the estimated opportunity your ads captured. A low share means the ads did not receive many of the impressions they were estimated to be eligible for, which points to a different question from low demand.
It is a diagnostic for visibility, not a goal on its own. Chasing a higher share can raise costs.
When it is useful
- Finding out whether limited budget or low ranking is capping visibility.
- Understanding how much more volume is available in a market you already compete in.
- Comparing visibility across campaigns that target similar searches.
Limitations
- The denominator is an estimate made by Google Ads.
- The reported figure depends on the report and segments you are viewing.
- A high impression share can still be unprofitable if the traffic does not convert.
Common mistakes
- Trying to calculate impression share from your own data.
- Raising bids to maximise share without checking cost and return.
- Comparing impression share between campaign types that report it differently.