How to Calculate PCC in a Speech Sample

Speech-language pathologists use the PCC -- percent consonants correct -- to determine what speech sounds a client is unable to produce. This measurement also helps the speech-language pathologist determine the severity of a client's speech disorder. PCC helps decide if a client is appropriate for speech therapy, as well as determine therapy goals. For a speech-language pathologist to accurately calculate PCC, a client must be able to produce multiple words for a lengthy speech sample.

Record with a digital voice recorder a communication sample of at least 100 words from the client. Use toys or pictures to elicit language from younger children. For older children or adults, ask open-ended questions or ask the client to describe an event or experience.

Transcribe the speech sample phonetically by hand or on a computer. Clearly indicate when the client produces consonants in error by highlighting incorrect pronunciations in a different color or using a specific symbol to denote errors.

Add up the total number of consonants and the total number of correct consonants. Divide the number of correct consonants by the total number of consonants. Multiply the answer by 100 to determine the PCC.

Use the PCC to determine the severity of the speech disorder. A percentage of 85 to 100 indicates a mild disorder; 65 to 85 percent, mild-moderate; 50 to 65 percent, moderate-severe; and below 50 percent, severe.