The Facebook Adult Reach Rate is a digital advertising metric that reflects the estimated percentage of a country’s adult population (ages 18 and above) that can potentially be reached through Facebook ads. It is calculated by comparing the number of Facebook users aged 18+ eligible to be targeted with ads to the total adult population in a specific country or territory. This metric helps advertisers assess the platform’s penetration among adults in a given region. When the reach rate exceeds 100%, it signals possible data discrepancies caused by factors such as users holding multiple accounts, incorrect or outdated age information in user profiles, or inaccuracies in population estimates. Despite these limitations, the Adult Reach Rate is a useful indicator for measuring Facebook’s advertising potential within demographic segments, especially in digital marketing and population-based outreach strategies.