How does Audience Size (1–10%) affect my Lookalike Audience?

Audience Size sets how closely your Lookalike Audience matches your source Custom Audience, versus how many people it reaches.

When creating a Lookalike Audience in our app, you'll set an Audience Size using a slider ranging from 1% to 10%, with 1% as the default.

1. In the Lookalike Audience creation form, drag the Audience Size slider to your preferred percentage.

What does the percentage mean? Meta builds your Lookalike Audience by finding people who share similar characteristics with your source Custom Audience, out of the total population in your selected target countries. The percentage you choose tells Meta how large a slice of that population to include.

• A smaller percentage (closer to 1%) gives you an audience that's a closer match to your source audience, but reaches fewer people.
• A larger percentage (closer to 10%) gives you a broader audience that reaches more people, but with a looser match to your source audience.

Which should you choose?

• Start with a lower percentage (1–2%) if accuracy matters most to you — for example, if your source Custom Audience is made up of past purchasers and you want the closest possible match.
• Use a higher percentage (up to 10%) if you want to scale your reach for broader brand awareness or top-of-funnel campaigns, and are comfortable with a less precise match.

2. Once you've set your Audience Size, finish the rest of the Lookalike Audience setup and click Create.

You can check the estimated number of people in your Lookalike Audience afterwards in the audience's details — see our article on viewing your audience details and estimated reach.

Updated on: 12/10/2026