Impression Share (IS)

Metric

Impression share is the percentage of eligible ad auctions in which your ad actually showed. The missing share splits into lost-to-budget (skipped auctions — needs money) and lost-to-rank (lost auctions — needs bids, quality or creative).

Layman Explanation & Analogy

Of every 100 customers who searched your keyword, impression share says in how many of those auctions your ad appeared. The two loss columns are the diagnosis: "lost to budget" means you could not afford your own demand; "lost to rank" means competitors beat your bid or your quality.

Mathematical Formula

Impression Share = Impressions Received / Total Eligible Impressions

Worked real-world example

A keyword shows 42% impression share: 12% lost to budget, 46% lost to rank. Raising the budget converts budget-losses into rank-losses at higher CPCs — the correct sequence is quality and bid work first, budget second.

What people get wrong & common traps

Chasing 95%+ share on generic keywords buys the most expensive marginal auctions and destroys CPA. Share is a diagnostic gate for budget and bid decisions, not a target — profitable accounts routinely sit at 60–75% on generics by choice.

Related terms