Lost impression share (budget) is the percentage of times your ads were eligible to show but did not, because the campaign’s budget had run out or Google was holding back spend to stay within it. In Google Ads it appears as “Search lost IS (budget)” for search campaigns and “Display lost IS (budget)” for display.
How lost impression share (budget) works
Google estimates how many impressions a campaign could have received, given its targeting, keywords, approval status and quality. Impression share is the proportion it actually received. Everything else was lost for one of two reasons, budget or rank, so impression share, lost IS (rank) and lost IS (budget) add up to 100%.
Losing impression share to budget does not only mean the campaign stopped at 3pm. Google spreads a daily budget across the day by entering fewer auctions, so a campaign can lose impressions in the morning without ever visibly running out. Because budgets are set on campaigns, this metric is most useful read at campaign level.
You will not see it by default. Add the competitive metrics columns to the campaigns view, or open them through the columns menu, and choose a date range of at least a few weeks. If several campaigns draw on one shared budget, the budget loss on each reflects how the shared pot was divided between them, not just its total size.
Why it matters
This is the figure that tells you whether more money could buy more of the same traffic. If a campaign produces enquiries at a cost you are happy with and loses a large share of impressions to budget, there are probably more enquiries available at a similar cost. That is a far better reason to raise spend than a general feeling that the ads are working.
As a made-up example, imagine a Leeds accountancy firm whose generic campaign spends £40 a day, produces leads at £35 each and shows “Search lost IS (budget)” of 45%. Nearly half the searches it was eligible for went unanswered. Raising the budget in steps, while watching whether the cost per lead holds, is a reasonable test. If the same campaign were producing leads at £150 each against a value of £80, the right move would be the opposite.
It also explains patterns that look like poor performance. A campaign that is limited by budget may show mostly early in the day, miss evening searchers, or drop out on your busiest days, when demand and competition both rise.
Common mistakes
- Raising the budget on a campaign that does not convert profitably. Buying more unprofitable clicks makes the problem bigger; fix the cost per result first.
- Overlooking the cheaper fix: lower bids or a tighter keyword list so the same budget buys more clicks, and better ones.
- Comparing brand and generic campaigns as if they should behave alike. A brand campaign should rarely lose impressions to budget; a generic one often does, and that can be fine.
- Judging from a single day. Budget loss varies by weekday and season, so look at several weeks.
- Treating 0% as the goal. A small, steady loss on a broad campaign can be a sensible cap on spend.
How to act on it
Read lost IS (budget) alongside cost per conversion or return on ad spend. If a campaign is profitable and losing a meaningful share to budget, raise the budget in steps and check that results hold at each step. If it is not profitable, keep the budget and tighten the campaign instead: remove poor search terms, reduce bids, pause weak keywords or limit the ad schedule to the hours that convert.
Then compare it with lost impression share (rank). A campaign losing heavily to both needs quality work as well as money, and extra budget alone will mostly buy the weaker positions. Deciding where each extra pound should go across campaigns is a core part of monthly PPC management.