https://stamurai.com/blog/understanding-degrees-of-stuttering-severity/ >How is the severity of a stutter measured? The severity or degree of stuttering is graded by most researchers by the percentage of syllables prolonged or repeated while speaking. Speech pathologists and therapists conduct tests to examine the ratio of non-stuttered and stuttered syllables in a conversation. The most prominent method of classification of the degrees of severity is as follows – >Less than 5% of syllables stuttered is considered mild. 5-10% is considered mild to moderate. 10-15% is considered moderate. 15-20% is considered moderate to severe. Above 20% is considered severe. Speech therapists and pathologists try to ensure that the child/adult being examined feels comfortable and willing to converse so as to get as accurate a result as possible But thats only the physical aspect of it. You can have a mild stutter with a severe mental aspect of it or a severe physical stutter were you dont care at all about it.