META ADS TOOL
Lookalike Audience Size Calculator
Estimate the reach of a Meta lookalike audience based on geography and percentage. Plus a readiness score for whether your seed is large enough.
Founder, BTB Audits. $150M+ in ad spend managed across Meta and Google
Before you build one: lookalikes are no longer the main targeting play. Broad and Advantage+ targeting now find buyers better, with your creative doing the filtering. Use a lookalike as a small experiment (about 10 percent of budget at most), not the backbone of the account. This tool sizes the audience if you decide a test makes sense.
Estimated audience reach
4.9M
United States · 2% lookalike
Seed readiness
UsableSeed size: 1,500 events
What this means for your account
Your seed meets Meta's minimum, but only barely.
1 percent lookalikes are workable. Above 3 percent the algorithm is extrapolating from limited signal. Consider building seed size before expanding lookalike percentage.
Want a senior pair of eyes on the specifics? The Free Quick Scan is a private 5 to 7 minute Loom in 48 hours.
Get Your Free Quick Scan →Learn the methodology
How this tool actually works
This calculator gives you the number. The paired blog post explains the math behind it, the edge cases, and how to read the result for your own account.
Read: Lookalike Audiences vs Interest Targeting in 2026 →Want a senior audit that uses lookalike audience size as the baseline for evaluating your account?
If you don't have four to six hours, or you want a second pair of eyes that's managed $150M+ across Meta and Google, the Free Quick Scan is what I built for that. I'll record a private 5 to 7 minute Loom walking through the leaks I find on your account using public data only. You'll have it in 48 hours.
Get Your Free Quick Scan →