Meta Lookalike Audiences: 100 Minimum, 1,000-5,000 Recommended

In short

Meta’s documented requirements for a lookalike audience:

• At least 100 people in the source audience — a hard floor.
• 1,000 to 5,000 people generally recommended.
• Up to 500 lookalike audiences from a single source.
• People in your source audience are excluded from the lookalike.
• Populating “can take up to 3 days”, though the audience is usable immediately.

The gap between the floor and the recommendation is the whole story. The hard floor is 10% of the bottom of Meta’s recommended range and just 2% of the top — an audience can therefore be technically valid and practically useless, and Meta will build it for you either way without warning.

The three behaviours that surprise people

Source members are excluded. A lookalike from your purchaser list will not contain your purchasers. This is correct — you already reach them through the custom audience — but it means “lookalike of purchasers” and “purchasers plus people like them” are different audiences, and campaigns built assuming the second will under-reach.

Location is no longer chosen at creation. Meta documents that you no longer select audience location when creating a lookalike, so new lookalikes show no estimated size in Audience Manager. The estimate appears when you use the audience in an ad set, and Meta uses the ad set’s location settings to find similar people. One saved lookalike now behaves differently in a UK ad set than in a US one. Existing lookalikes were not affected by the change.

Populating is not blocking. You can run ads with an audience in the populating state, and Meta warns the size “will increase as the audience is populated”. An early read on performance is taken against an audience that is still growing, which makes day-one numbers unreliable in a way that has nothing to do with the learning phase.

Source quality beats source size

The recommendation to use 1,000–5,000 is about signal density, not volume. A source of 5,000 undifferentiated site visitors describes “people who visited a website” and produces a lookalike of approximately everyone. A source of 1,200 repeat purchasers describes something specific.

If you have the volume, the useful move is to narrow before you expand: build the source from the highest-value behaviour you have enough of, rather than the largest list you can assemble. Meta’s 500-lookalikes-per-source allowance exists precisely so you can build several from one well-defined source rather than one from a vague one.

The custom audience limits worth knowing alongside

For website custom audiences — the usual lookalike source — Meta documents two constraints that shape what you can build:

• Up to 5 rules per audience.
• The audience starts populating from the time you create it and does not backfill.

The second is the one that costs time. A website custom audience created today contains nobody from last month. If you intend to build a lookalike from 180-day purchasers, that audience needed to exist 180 days ago.

Put a number on the delay and it stops sounding abstract. A brand adding 300 purchasers a month reaches Meta’s 100-person floor in about 10 days, but reaches the bottom of the recommended 1,000–5,000 range in roughly 3.3 months and the top in 16.7 months. Starting the audience the day you read this rather than the day you need it is worth over a year of waiting, and the audience costs $0 to create and nothing to hold.

Interpretation boundary

These are Meta’s documented requirements as retrieved on 2026-09-22, and Meta notes separately that lookalike audiences are limited or unavailable for some ads about financial products, employment or housing, and that targeting options are restricted for audiences including people under 18. The 1,000–5,000 figure is Meta’s general recommendation, not a validated optimum for any particular account — it is a starting point to test against, not a rule.

Can software help?

Bach.ai audits your connected Meta account, estimates the revenue impact of what it finds, and proposes specific fixes. It applies a change only after you approve it. Think of it as an automated audit layer that surfaces issues and proposed fixes for your review — not a replacement for your team’s judgment, and creative production is not its core job, though the Pro and Agency plans can generate a limited number of variants.

FAQ

What is the minimum size for a Meta lookalike source audience?

100 people is the documented hard floor. Meta generally recommends between 1,000 and 5,000, which is ten to fifty times the minimum — an audience can be technically valid and practically useless.

Are my source audience members included in the lookalike?

No. Meta documents that people in your source audience are excluded from the lookalike. A lookalike of purchasers contains no purchasers, so it is not a substitute for also targeting the source list.

How many lookalikes can I create from one source?

Up to 500 from a single source audience. That allowance exists so you can build several well-defined lookalikes from one high-quality source rather than one from a vague list.

Why does my website custom audience have no historical data?

Because Meta documents that it starts populating from the time you create it and does not backfill. A 180-day purchaser audience needed to exist 180 days ago; creating the audiences you will want later costs nothing now.

Method and sources

“Meta documents a hard minimum of 100 people in the source, and generally recommends a source audience of between 1,000 and 5,000.”

Source: Meta Business Help Centre, retrieved 2026-09-22:

• https://www.facebook.com/business/help/465262276878947
• https://www.facebook.com/business/help/1474662202748341

Meta’s documentation changes without notice and these thresholds have moved before — verify anything load-bearing against the current version of the article before you act on it.