The Stuttering Severity Instrument is a standardized assessment used by speech-language pathologists (known as speech-language therapists in some jurisdictions) to evaluate the severity of a person’s stutter. 

The assessment covers the frequency of stuttering in both reading and speech, the duration of moments of stuttering, and the secondary behaviours associated with the stuttering. Each is rated independently of the others on a specified scale, and the total scores are added to achieve an overall severity rating.

The SSI describes clearly the degree to which primary and secondary behaviours of stuttering are present in an individual’s speech. It does not, however, assess how severely an individual is impacted by their stutter. For some, a “moderately-severe” stutter may feel like nothing more than a mild nuisance, or may even be a point of pride. For others, a mild stutter has a profound impact on their daily lives. Additional assessments would be needed to address the impact of a stutter.