Rex says
The fast lane for the math you almost remember from school. Type the numbers, get the answer, move on with your day.
Try a scenario
Click to load — tweak from there.Inputs
Result
Extra monthly budget to capture lost-budget IS
$4,364
Additional clicks available
2,182
Impressions missed due to budget
54,545
Total eligible impressions (full auction)
181,818
Impression share if budget unconstrained
85%
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How to use this
- 1Enter current impression share (%).
- 2Enter lost is (budget) (%).
- 3Enter lost is (rank) (%).
- 4Enter current monthly impressions.
- 5Enter current monthly clicks.
- 6Enter current monthly spend ($).
- 7Read your extra monthly budget to capture lost-budget is on the right — it updates as you type.
- 8Hit Share to keep the scenario or send it to someone.
About this calculator
Impression share tells you what percentage of eligible auctions your ad actually showed in, and Google Ads splits the losses into two buckets: lost to budget (you'd have shown but ran out of daily budget) and lost to rank (your ad rank wasn't competitive enough even with budget available). This calculator takes your current impression share, budget-lost and rank-lost percentages, current spend and clicks, and estimates the additional clicks and spend needed to fully capture the budget-lost share — since that's the lever you control directly by raising budget, versus rank-lost share which requires bid or quality score improvements. It computes total eligible impressions implied by your current share, the click volume you're leaving on the table from budget constraints specifically, and the proportional budget increase required to close that gap, assuming a flat cost-per-click. This only estimates the budget-lost opportunity because rank-lost share isn't solved by spending more; it requires improving ad relevance, landing page experience, or bids, which don't scale linearly and can't be modeled with a simple formula.
Worked example
Using the values the calculator loads with:
Inputs
- Current impression share: 55 %
- Lost IS (budget): 30 %
- Lost IS (rank): 15 %
- Current monthly impressions: 100000
- Current monthly clicks: 4000
- Current monthly spend: 8000 $
Results
- Extra monthly budget to capture lost-budget IS: $4,364
- Additional clicks available: 2,182
- Impressions missed due to budget: 54,545
- Total eligible impressions (full auction): 181,818
- Impression share if budget unconstrained: 85%
What each field means
Inputs
- Current impression share (%)
- The current impression share used in the calculation, measured in %. Starts at 55 % so you have a working example on load. Accepted range: 1–100 %.
- Lost IS (budget) (%)
- The lost is (budget) used in the calculation, measured in %. Starts at 30 % so you have a working example on load. Accepted range: 0–99 %.
- Lost IS (rank) (%)
- The lost is (rank) used in the calculation, measured in %. Starts at 15 % so you have a working example on load. Accepted range: 0–99 %.
- Current monthly impressions
- The current monthly impressions used in the calculation. Starts at 100000 so you have a working example on load.
- Current monthly clicks
- The current monthly clicks used in the calculation. Starts at 4000 so you have a working example on load.
- Current monthly spend ($)
- The current monthly spend used in the calculation, measured in $. Starts at 8000 $ so you have a working example on load.
Results
- Extra monthly budget to capture lost-budget IS
- Returned as a money amount in US dollars and shown as the headline result. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Additional clicks available
- Returned as a whole number. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Impressions missed due to budget
- Returned as a whole number. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Total eligible impressions (full auction)
- Returned as a whole number. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Impression share if budget unconstrained
- Returned as a percentage. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
FAQ
What's the difference between lost IS (budget) and lost IS (rank)?
Lost IS (budget) means your ad would have been shown and was competitive, but your daily budget ran out before the auction happened. Lost IS (rank) means even with budget available, your ad rank — a combination of bid and quality score — wasn't high enough to show. Only the budget bucket is solved by raising spend.
Is it always worth raising budget to capture lost-budget impression share?
Only if the marginal clicks convert profitably. Budget-constrained campaigns typically exhaust budget on the best-performing hours and keywords first, so the marginal impressions you'd pick up by raising budget are often lower-intent than your current traffic — model the additional spend against a slightly lower expected conversion rate, not your blended average.
How do I fix lost IS (rank) instead?
Improve quality score by tightening ad-to-keyword relevance and landing page experience, or raise bids on the specific keywords with high rank loss. Quality score improvements are cheaper long-term than just outbidding competitors, since a higher quality score lowers your effective CPC for the same rank position.
Why does this only estimate clicks, not conversions?
Conversion rate on the marginal budget-lost impressions is unknown and often differs from your current average, since budget typically runs out after your best-performing time windows or audiences have already been served. Treat the additional clicks figure as an upper bound and apply your own judgment on conversion rate before projecting revenue.
Accuracy and limitations
- Results are rounded for display; the underlying calculation keeps full precision.
- Very large or very small inputs may hit floating-point limits in the browser.
- Inputs outside the accepted range are clamped rather than rejected.
Related tools
Cite this calculator
Writing about this topic? Grab a citation — every link helps keep these tools free.
RevenueLab. (2026). Paid Search Impression Share & Lost IS Calculator. Retrieved from https://www.revenuelab.fyi/toolbox/paid-search-impression-share-calculator
<p>Source: <a href="https://www.revenuelab.fyi/toolbox/paid-search-impression-share-calculator" target="_blank" rel="noopener">Paid Search Impression Share & Lost IS Calculator — RevenueLab</a> (2026).</p>
Source: [Paid Search Impression Share & Lost IS Calculator — RevenueLab](https://www.revenuelab.fyi/toolbox/paid-search-impression-share-calculator) (2026).