Prevalence rates of autism based upon child samples have shown a consistent increase over the past three decades, suggesting that many autistic adults are undiagnosed. Adult diagnostic pathways typically are initiated with measures of autistic-like traits. Whilst autistic-like traits represent a continuous dimension across the general population, autism is a categorical diagnosis and the relationship between the two is unclear. A self-report dimensional reflection upon the two diagnostic criteria for autism was developed and reflected upon by 1076 participants embedded within two online surveys. Those with an informal (self) diagnosis of autism self-reported comparable social difficulties but fewer restricted and repetitive behaviour difficulties than those with a formal diagnosis of autism. The new items also significantly correlated with autistic-like traits.