Glossary
What is ad impression share in Keyword Planner?
Melvin Salas1 min readVerified 5 October 2026
Short answer
Ad impression share in Keyword Planner is, in Google's words, the number of impressions that you've received divided by the total number of searches for the location and network that you're targeting that matched the keyword exactly in the last calendar month.
Google says it is different from the impression share and exact match impression share columns in campaign management, which are based on the number of impressions that you were eligible to receive for a keyword. In Keyword Planner, ad impression share is based on the search volume for that exact keyword.
So the two divide by different things. The campaign column divides by the impressions you were eligible to receive. The Keyword Planner column divides by the exact-match searches for the location and network you target in the last calendar month. Google says that when you see a dash (-) in the ad impression share column, there isn't enough data to calculate this number.
Our reading, not Google's: the two figures for the same keyword are not a check on each other. A low Keyword Planner figure beside a high campaign figure is not a contradiction, because the campaign figure leaves out searches the campaign was never estimated to be eligible for.
Reading these columns is daily work for us
Riibon watches every campaign daily and holds a baseline for each metric, so a move in impression share or Quality Score is judged against what is normal for that account, not against a rule of thumb, before anyone acts on it.
Ask the Riibon app whether your campaigns are losing to budget or to rank. It is free, with no time limit and no card. Or book a call and we run it for you.