There are many factors that impact intelligibility, or how easy it is to understand someone who is speaking. A young child learning how to talk will be much more unintelligible than an older child who is mastering their speech. Speech intelligibility in children increases as a child ages, with most children being quite intelligible by 7 years of age.

Scroll to the bottom of this post to download a Speech Intelligibility Norms PDF!

What is Speech Intelligibility?

Speech intelligibility is how clear or understandable speech is to others. In other words, when someone is speaking to you, how much of what they’re saying can you understand?

Intelligibility in adults is often dependent on many factors – including background noise, the complexity of the conversation, differing accents or dialects, and more. Adults are not always 100% understandable or clear when speaking to others, and something like loud noise at a party can make it more difficult to understand your communication partner.

Intelligibility in children improves with age and speech and language development. Younger children are more unintelligible (difficult to understand) as they have not mastered all speech sounds and rules of language. Children are often more intelligible to parents and those whom they communicate with frequently versus strangers. Additionally, children with speech and language delays, hearing loss, genetic syndromes, or other disorders are likely to have lower speech intelligibility than their peers.

Speech Intelligibility by Age

In a 2021 study on speech intelligibility in children, Hustad et al. sampled the speech of 538 typically developing children, had a group of 1,076 adults transcribe the speech samples, and used this information to calculate single-word and multi-word intelligibility.

Results from the study found that the average child should be at least 50% intelligible by 4 years old (meaning you should be able to understand about half of what a 4-year-old is saying when they speak to you) and 90% intelligible by 7 years old. Other speech intelligibility norms from this study include the following:

  • 25% intelligible by 3 years old
  • 50% intelligible by 4 years old
  • 75% intelligible by 5 years old
  • 90% intelligible by 7 years old

Important Note: These percentages are based on unfamiliar listeners with unknown contexts. An unfamiliar listener is someone who does not communicate with that person on a regular basis. Parents can expect their children to be more intelligible than these reported numbers since they are familiar with their children’s speech. Children will also be more intelligible, or understandable if the listener understands the context – the situation in which the conversation is taking place.

Keeping these caveats in mind, the following intelligibility percentages are likely to be HIGHER for parents and those who understand the context (the environment or situation that helps clarify the meaning) of what the child is saying.

Collage showing speech intelligibility from age 3 to age 10.Speech Intelligibility Norms

As previously mentioned, a child’s intelligibility should improve as they get older. While 2- and 3-year-olds are still fairly difficult to understand, older school-age children 7 years old and older should be 90-100% understandable.

Here’s a closer look at intelligibility with unfamiliar listeners by age:

Chart showing children are 25% intelligibility by age 3.

3 Years Old

A 3-year-old’s speech is approximately 25% intelligible to unfamiliar listeners. Intelligibility improves the fastest between 2 1/2 to 3 1/2 years of age. If you have a 2-year-old who is very difficult for others to understand, you can anticipate a major growth over the next year or two with them being much easier to understand by the time they are 4 years old.

A 3-year-old’s intelligibility ranges between the following:

  • Single words: 24% – 48% intelligible
  • Sentences: 12% – 41% intelligible

As you can see, there is quite a range in how understandable 3-year-olds should be, especially when they are speaking in sentences. This lower intelligibility is still age-appropriate and will continue to improve into their 4th year.

Chart showing children are 50% intelligibility by age 4.

4 Years Old

A 4-year-old’s speech is approximately 50% intelligible to unfamiliar listeners. As a quick rule of thumb, a 4-year-old is about 50% intelligible to unfamiliar listeners. A family member or someone who communicates with a 4-year-old very often should expect that child to be over 50% intelligible.

A 4-year-old’s intelligibility ranges between the following:

  • Single words: 44% – 67% intelligible
  • Sentences: 41% – 69% intelligible

Chart showing children are 75% intelligibility by age 5.

5 Years Old

A 5-year-old’s speech is approximately 75% intelligible to unfamiliar listeners. When a child turns 5 years old, they should be about 75% intelligible to an unfamiliar listener. Remember, that it is likely they will be more intelligible to parents, siblings, and other close individuals, so if a parent or caregiver is not understanding over half of what their child is saying, there may be cause for concern.

A 5-year-old’s intelligibility ranges between the following:

  • Single words: 59% – 79% intelligible
  • Sentences: 66% – 85% intelligible

Chart showing children are 85% intelligibility by age 6.

6 Years Old

A 6-year-old’s speech is approximately 85% intelligible to unfamiliar listeners. Six-year-olds are around 80% intelligible when speaking to others. From the ages of 6 and up, children are fairly understandable when they speak to others, but they still have some growth to make in the next few years to get them closer to being 100% intelligible.

A 6-year-old’s intelligibility ranges between the following:

  • Single words: 68% – 86% intelligible
  • Sentences: 79% – 92% intelligible

Chart showing children are 90% intelligibility by age 7.

7 Years Old

A 7-year-old’s speech is approximately 90% intelligible to unfamiliar listeners. By 7 years of age, we should expect children to be around 90% intelligible. This means most words and sentences a 7-year-old says should be understandable with a very small portion of their speech unintelligible.

A 7-year-old’s intelligibility ranges between the following:

  • Single words: 73% – 89% intelligible
  • Sentences: 87% – 95% intelligible

Chart showing children are 94% intelligibility by age 8.

8 Years Old

An 8-year-old’s speech is approximately 94% intelligible to unfamiliar listeners. Intelligibility continues to improve after 7 years, albeit at a much slower pace. As you can see in the next 3 ages, intelligibility only increases by a percentage or two each year.

An 8-year-old’s intelligibility ranges between the following:

  • Single words: 76% -91% intelligible
  • Sentences: 91% – 97% intelligible

Chart showing children are 96% intelligibility by age 9.

9 Years Old

A 9-year-old’s speech is approximately 96% intelligible to unfamiliar listeners. There is little change in intelligibility from 8 years of age to 9 years of age, but you can expect a slight improvement in how much of a child’s speech unfamiliar listeners understand.

A 9-year-old’s intelligibility ranges between the following:

  • Single words: 77% – 91% intelligible
  • Sentences: 94% – 98% intelligible

Chart showing children are 97% intelligibility by age 10.

10 Years Old

A 10-year-old’s speech is approximately 97% intelligible to unfamiliar listeners. By the time a child celebrates their 10th birthday, you can expect them to be highly intelligible. Most teenagers and adults are never 100% intelligible, so you can expect to understand a 10-year-old very well.

A 10-year-old’s intelligibility ranges between the following:

  • Single words: 78% – 93% intelligible
  • Sentences: 95% – 98% intelligible

Speech Intelligibility Norms Chart

This speech intelligibility norms chart is a great download to quickly reference the sentence-level intelligibility of English-speaking children. All norms are reference-based and updated with the most recent information available.

Click on the image below to download the speech intelligibility norms PDF.

Speech Intelligibility chart with download button overlay.

Is Your Child Difficult to Understand?

These intelligibility norms are a guideline for teachers, parents, and speech-language pathologists to use to assess a child’s speech development. Many other considerations should be taken when determining if a child’s speech and communication development is on track.

Remember! These intelligibility norms indicate sentence-level intelligibility of English-speaking children with unfamiliar listeners in unknown contexts. If a familiar listener (such as a close family member or friend) is having difficulty understanding a child at the percentages listed above, it may be beneficial to reach out to a licensed speech therapist in your area.

If you have concerns about your child’s speech, please contact us or speak with a local speech-language pathologist for further information and recommendations.

More Speech Norms

Interested in learning more about speech norms and speech pathology? Check out these posts below!

Sources

Hustad, K.C., Mahr, T.J., Natzke, P., & Rathouz, P.J. (2021). Speech development between 30 and 119 months in typical children I: Intelligibility growth curves for single-word and multiword productions. Journal of Speech, Language, and Hearing Research. https://doi.org/10.1044/2021_JSLHR-21-00142

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