Paid media
Size your addressable retargeting audience from traffic, window and match rate.
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- Claude, via MCP
How big will my retargeting audience be, and what budget does it need?
Pool size = monthly unique visitors × (window in days ÷ 30) × match rate. Monthly impressions = pool × weekly frequency × 4.33, and budget = impressions ÷ 1,000 × CPM. With 25,000 visitors, a 30-day window and 55% match, the pool is 13,750; four impressions a week at a ₹150 CPM needs about ₹35,700 a month.
Around 13,750 addressable users. Budget near $2,143/month sustains ~4× weekly frequency without over-serving.
Match rate is where most retargeting math breaks, post-iOS and consent loss routinely cut addressable pools by 30–50%.
About this calculator
A retargeting audience that looks big on paper is often much smaller once you account for how much of your traffic is actually addressable after consent frameworks and pixel loss. This calculator sizes your durable, reachable retargeting pool from real traffic and match-rate inputs, then tells you the minimum budget to actually maintain a healthy frequency against it.
How to use it
- Enter your monthly unique visitors and the retargeting window in days, how long you keep someone in the audience after they visit.
- Enter your cookie or match rate, the share of visitors who remain identifiable and addressable for ads post-privacy changes.
- Enter your target weekly frequency and your retargeting CPM.
- Read the addressable pool size, the monthly impressions needed to hit your target frequency, and the suggested minimum monthly budget.
Methodology
The raw pool scales monthly unique visitors by window ÷ 30, so a 60-day window roughly doubles the rolling pool versus a 30-day window, and a 7-day window shrinks it to about a quarter.
That raw figure is then multiplied by match rate, since not every visitor remains identifiable and reachable for retargeting after browser and platform privacy restrictions.
Monthly impressions needed is pool size × target weekly frequency × 4.33 (average weeks per month), the delivery volume required to hit that frequency evenly across the whole pool.
Minimum budget is that impression volume ÷ 1,000 × CPM, a floor budget assuming even delivery. Below roughly 1,000 addressable users, the calculator flags the pool as thin, standalone retargeting struggles to sustain frequency or find enough inventory at that scale.
Retargeting pool, impressions and minimum budget
Raw pool = Monthly unique visitors × (Window days ÷ 30) Addressable pool = Raw pool × Match rate Monthly impressions = Addressable pool × Weekly frequency × 4.33 Minimum monthly budget = Monthly impressions ÷ 1,000 × CPM
- Monthly unique visitors
- Unique users per month from your analytics tool.
- Window days
- How long a visitor stays in the retargeting audience after their visit.
- Match rate
- Share of visitors the ad platform can still identify and reach, after consent refusals, browser restrictions and ad blockers.
- Weekly frequency
- Impressions you want each person in the pool to see per week.
- CPM
- Cost per 1,000 impressions for retargeting on the platform.
Scaling by window ÷ 30 assumes visitors in different months are mostly different people. Returning visitors overlap, so long windows overstate the pool. The match rate is the biggest unknown: compare the audience size the platform reports with your visitor count over the same window to estimate it. Below about 1,000 people the tool flags the pool as thin.
Worked example: a B2B site with 25,000 visitors a month
A B2B software company gets 25,000 unique visitors a month. It wants to retarget visitors from the last 30 days on Meta, showing each person about four ads a week. Its Meta audience shows about 55% of visitors are matched, and retargeting CPMs run at about ₹150.
- Raw pool = 25,000 × (30 ÷ 30) = 25,000.
- Addressable pool = 25,000 × 55% = 13,750.
- Monthly impressions = 13,750 × 4 × 4.33 = 2,38,150.
- Minimum budget = 2,38,150 ÷ 1,000 × ₹150 = ₹35,723 a month.
- With a 60-day window the pool doubles to 27,500 and the budget for the same frequency to about ₹71,400.
About ₹36,000 a month covers the 30-day pool at four impressions a week. Spending much more mainly raises frequency on the same people. Extending the window adds people, but older visitors are usually less likely to convert, so consider a separate, lower-frequency ad set for days 31 to 60. Check frequency once live with the ad frequency risk checker.
Minimum audience sizes on Google Ads
| Network | Minimum active users in the last 30 days |
|---|---|
| Google Display Network | 100 |
What is a good retargeting pool size?
Big enough to deliver consistently, small enough to stay relevant. Practical checks:
- Above the platform minimum, or the ads will not serve at all.
- Above about 1,000 people for a standalone campaign, the tool's threshold for a pool that can sustain delivery.
- Segmented by intent once it is large: pricing-page and demo-page visitors deserve more frequency than blog readers.
If the pool is thin, spend on growing traffic first, or combine retargeting with a lookalike of the same visitors.
Retargeting in India vs the US
Retargeting CPMs in India are low, so even modest budgets reach high frequency quickly; cap frequency or add creative variety. Many Indian visitors browse on mobile apps and in-app browsers, which can lower match rates. WhatsApp follow-up for known leads is often cheaper than paid retargeting for the same people, so retarget only those you cannot reach directly.
US match rates are affected by browser tracking prevention, consent tools and ad blockers, so pools are often much smaller than visitor counts. Server-side events through the Conversions API and customer-list audiences recover part of the gap. For B2B, retargeting account lists on LinkedIn is a common complement.
Common retargeting mistakes
- Treating total visitors as the audience size and budgeting for people the platform cannot reach.
- Using one long window with one message for everyone, regardless of what they viewed.
- Not excluding recent buyers or current customers, which wastes spend and annoys them.
- Setting a budget far above what the pool needs, which only raises frequency.
- Counting returning visitors twice when stretching the window.
Sources
- How your data segments work, Google Ads Help. Accessed 2026-10-19.
- Conversions API, Meta for Developers. Accessed 2026-10-19.
FAQ
Match rate does most of the damage here. Post-iOS App Tracking Transparency and cookie consent frameworks routinely cut addressable audiences by 30-50% compared to raw traffic, so the number people expect (total monthly visitors) and the number platforms can actually reach diverge significantly.
Pull it from your ad platform's audience size reporting versus your analytics traffic for the same period, that ratio is your real match rate, and it will typically be lower on mobile web and iOS traffic than on desktop.
Widen the retargeting window if your sales cycle allows it, feed the pool with more top-of-funnel traffic, or fold it into a broader lookalike or prospecting-plus-retargeting blend rather than running it as a standalone, undersized audience.
A 90-day window captures far more people, but many of them saw your site three months ago and have cooled off. Balance pool size against recency, a smaller, fresher pool often converts better than a larger, stale one even though this calculator only sizes volume, not intent decay.
Match it to your buying cycle. Short windows (7 to 30 days) suit fast decisions such as e-commerce; longer windows (60 to 180 days) suit B2B with long cycles. Split long windows into stages with different messages and frequency.
Platforms can only match visitors they can identify. Consent refusals, browser restrictions, ad blockers and logged-out users all reduce the match, so the audience is a fraction of total visitors.
Usually yes, for the offer they already took. Move them into a separate audience for upsell or onboarding messages instead.
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