Retargeting Pool Size Estimator
Size your addressable retargeting audience from traffic, window and match rate.
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.
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.