Impression Share Calculator
Measure the share of available auctions you actually won, and separate the share you lost to BUDGET from the share you lost to RANK — because only one of them is solvable with money.
Impression Share Calculator
Results recalculate instantly on every keystroke. Nothing you type is transmitted.
What this result does not account for
- Eligible impressions is a platform estimate, not a measured count.
- Assumes lost auctions would convert like the ones you win, which is optimistic.
- Impression share is bounded by your own targeting, not the whole market.
In short: The two losses are different problems. Winning 1,000,000 of 1,650,000 eligible impressions is 60.6061% share; 18% lost to budget is buyable for 7,417.58 and worth 853.19 of profit, while 21.3939% lost to rank is not.
Formula
impression share = won ÷ eligible
won% + lost to budget% + lost to rank% = 100%
[('impression share', 'auctions won as a share of eligible'), ('lost to budget', 'eligible, unaffordable — buyable'), ('lost to rank', 'entered and lost — not buyable'), ('the identity', 'the three shares always sum to 100%')]
Worked Example
- Divide impressions won by impressions eligible.
- Take the budget-lost share from the platform report.
- Derive the rank-lost share as the residual.
- Price the budget loss in clicks, revenue and profit.
- Treat the rank loss as a quality problem, not a budget one.
1,000,000 impressions from 1,650,000 eligible is a 60.6061% share. With 18% lost to budget, the rank loss is the residual 21.3939% — and the three sum to exactly 100%. The budget loss is 297,000 impressions, which at a 1.85% CTR is 5,494.50 clicks costing 7,417.58, producing 153.85 conversions worth 19,692.29 of revenue and 853.19 of profit after the media. That is buyable. The 353,000 impressions lost to rank are not — they need bid, relevance or landing page work instead.
Strengths & Limits Of This Model
Where this engine is strong
- Derives the rank residual so the identity always holds
- Prices the budget loss in profit, not just impressions
- States when a low share is the correct outcome
Where it stops
- Platform-estimated denominator
- Optimistic conversion assumption
Practical Use Cases
Justifying a budget increase
Pricing the profit sitting in the budget gap.
Diagnosing a share problem
Splitting budget loss from rank loss.
Auction competitiveness
Sizing how much of the market you actually reach.
Deciding against more budget
Finding when the constraint is protecting you.
Prioritising quality work
Quantifying the unbuyable share.
Methodology & Editorial Standards
Impression share is impressions won over eligible impressions, and the rank-lost share is DERIVED as the residual so the three-way identity holds by construction rather than by assumption. Where the entered budget loss is inconsistent with the computed share the page refuses to report rather than showing a negative residual. The budget-lost share is priced through the full funnel into revenue and profit, because the decision it informs is whether the incremental spend is worth making, and the page states plainly when the answer is no.
Computation runs in IEEE-754 double precision at full internal precision; rounding to two decimal places occurs strictly at the display layer, so no cumulative drift enters the result. All monetary outputs use accounting presentation — grouped thousands, two decimals, negatives in parentheses — so figures can be transcribed directly into a model or working paper. Division-by-zero and out-of-domain inputs return an em-dash rather than a misleading number.
This engine was reconciled against an independent reference implementation and hand-verified for the worked example above before release. Our full five-stage review process is published on the About Us page.
Disclaimer. This calculator is provided for informational and modelling purposes only and does not constitute financial, tax, legal, medical, or engineering advice. Verify all figures with a qualified professional before acting on them.
Impression Share Calculator — 10 Expert FAQs
10 analyst-written answers to the questions practitioners actually ask — optimised for voice and answer-engine retrieval.
What is impression share?
The share of auctions you were eligible for that your ad actually appeared in. It is the clearest measure of how much of the available market you are reaching, and its complement splits into two very different problems.
What is the difference between lost to budget and lost to rank?
Budget loss means you were eligible and the money ran out, so more budget captures those auctions directly. Rank loss means the auction ran, you were in it, and you lost on bid or quality. No amount of budget fixes the second.
Do the three shares always sum to one hundred?
Yes, by construction. Impression share plus share lost to budget plus share lost to rank must equal one hundred per cent. If your figures do not, they cover different periods or different campaign sets.
Should I always try to increase impression share?
No. A hundred per cent share usually means you are bidding on traffic that does not pay for itself. The right test is whether the incremental impressions return more than they cost, and sometimes a budget constraint is protecting you from unprofitable volume.
How do I improve rank-lost share?
Raise your bid, or improve the quality signals — expected click-through rate, ad relevance and landing page experience. The quality route is strictly better because it raises rank and lowers your cost per click simultaneously, while bidding raises rank and raises costs.
What is absolute top impression share?
The share of eligible auctions where your ad appeared in the very first position above the organic results. It cannot exceed your overall impression share, and the gap between them tells you how often you appear but appear low.
Is eligible impressions an exact figure?
It is a platform estimate of the auctions your targeting made you eligible for, not a measured count. Treat it as directional and consistent within a platform, rather than as a precise market size you can bank on.
Does a low impression share always mean I am losing?
Not if the traffic you are missing would not have paid for itself. Highly targeted accounts often run modest impression share deliberately, capturing the profitable segment of a large market rather than all of a small one.
How does impression share relate to market share?
They are related but not the same. Impression share measures auction presence within your own targeting, which may be a narrow slice of the total market. Broadening targeting lowers impression share while potentially increasing actual reach.
Can I have high impression share and poor performance?
Easily, and it is common in small niches. Winning nearly every auction in a market that is too small to matter produces an impressive share and very little revenue. Share is a measure of presence, not of demand.