PurposeEpidemiological research of stuttering has frequently focused on children, with a relative paucity of population level data specific to adults. Prevalence data for adults are reassessed here, including a breakdown of whether stuttering is overt or covert, and whether onset was in childhood or adulthood. The engagement of adults who stutter with stuttering communities is also estimated. MethodsPrevalence calculations were based on data from studies having the strongest designs, following the systematic review of Gattie, Lieven & Kluk (2024, this issue). Original data for engagement with stuttering communities were gathered from English language internet stuttering support groups, a national stuttering charity in the UK and a regional stuttering support group in Manchester, UK. ResultsAdult stuttering prevalence was estimated at 0.96% (95% CI 0.65, 1.44). This can be broken down to 0.63% overt stuttering (95% CI 0.46, 0.79) comprising 0.53% childhood onset and 0.10% adult onset; and 0.33% covert stuttering (95% CI 0.19, 0.58) comprising 0.28% childhood onset and 0.05% adult onset. Covert stuttering will have been overestimated, and may often be very mild. Engagement with stuttering communities was estimated at 0.99% internationally, 0.63% nationally and 1.01% regionally. Actual engagement will have been lower due to attrition and overcounting. ConclusionThe adult stuttering prevalence estimate of 0.96% is consistent with the widely-cited all ages stuttering prevalence estimate of 1%. Of adults who stutter, fewer than 1% engage with stuttering communities.