Your kid says “I fink so” instead of “I think so,” or “dat one” instead of “that one,” and part of you wonders whether this is the sound you should start working on, especially if the R, S, and L sounds already seem to be coming along.
So, what age should kids say the TH sound? There are actually two “th” sounds, and they arrive at different times. Most children say the “th” in this, that, and the by about age 5¾, and the “th” in thumb and three by about 6½. TH is one of the very last sounds to develop, so “fumb” for “thumb” is normal in the early years. If it’s still swapped after age 7, or you’re wondering sooner, a speech-language pathologist can take a look.
Typical ages for the TH sound
These ages come from a review of studies of US English-speaking children. They show when about 90% of children say the sound clearly. Think of them as a guide, not a deadline.
| Age | What’s typical |
|---|---|
| 3–5 | F, D, or S for TH is very common (“fumb,” “dis”). |
| ~6 | Most children (90% by about 5¾) say the “th” in this, that, the. |
| 6½ | Most children (90% by about 6½) say the “th” in thumb, three. |
| 7+ | If TH is still being swapped, it’s a good time to ask. |
You’ll often see “7” online as the age for TH. That’s a fair outer edge for the harder “th” in thumb, and some children do take until then.
What you might hear
The two sounds feel almost the same in your mouth, with the tongue tip resting lightly between the teeth. The difference is the voice. For this you use your voice (voiced). For thumb you only blow air (voiceless). Common swaps while they develop:
- fumb for thumb, free for three (F for voiceless TH)
- dis for this, dat for that (D for voiced TH)
- muvver for mother (V for voiced TH)
- sing for thing (S for voiceless TH)
When to ask a speech-language pathologist
You don’t have to wait for a certain age to ask. If you’re wondering, ask. A speech-language pathologist (SLP) can tell you whether what you’re hearing is typical and what, if anything, to do next. Good reasons to check in:
- TH is still being swapped after age 7
- TH swaps come along with other sounds that are hard to understand
- Family, friends, or teachers often can’t understand your child
- Your child seems frustrated, or avoids talking
- You have any concern about hearing
Your pediatrician can point you to an SLP, and many public schools offer free screenings.
What to do tonight
- Say it back the natural way. If your child says “fumb,” you say, “Yes! A thumb!” No "say it again," no quiz.
- Read together. A few minutes, a few times a week, with a story that has lots of the sound.
- Make it a conversation. Ask about the pictures, add a little to what your child says, and ask again. ("What’s that?" "A truck." "Yes, a big red truck! Can you spot another one?") My mom put a research sheet on this, called dialogic reading, at the back of the original Chatter Batter books, and it still holds up.
- Keep it warm. A child who feels loved is more willing to keep trying.
The American Academy of Pediatrics recommends shared reading from birth through at least kindergarten, so there’s no wrong time to start.
Get it as an instant digital download and read it together tonight → Thing-a-ma-Jig and Thing-a-ma-Bob
This is exactly why we made Thing-a-ma-Jig and Thing-a-ma-Bob. It’s the story of twin brothers who hatched from the same egg, who can cook breakfast and wash dishes just fine, but can’t spell their own names, and school starts this Thursday. Thing-a-ma-Jig spends the whole book worried, right up until his brother tells him, “Don’t worry, brother, that’s what school is for. We’ll have a teacher that will teach us to think big thoughts.” He finally settles down to sleep, and immediately discovers a brand new worry (he can’t tie his shoes!) while Thing-a-ma-Bob just keeps snoring beside him. Every “th” in the story is highlighted right on the page, so your child gets the practice while you’re just reading together about two brothers who love each other through every worry.
Not sure TH is the sound to focus on yet? Take the free 60-Second Sound Check first. It’s not a screening, just a quick way to notice what your child is still growing into.
Frequently asked questions
Is it normal for a 5-year-old to say F for TH?
Yes. F for the “th” in thumb (fumb) is one of the most common swaps. About 90% of US children say it by about 6½.
Are there really two TH sounds?
Yes. There’s a voiced TH (this, that, mother) and a voiceless TH (thumb, three, bath). Voiced TH tends to come in a little earlier.
When should I ask about TH?
If TH is still swapped after age 7, if other sounds are also hard to understand, if your child seems frustrated, or if you have hearing concerns. Asking earlier is fine too.
Read Next
Should I wait to see if my child outgrows a speech sound?
What Age Should Kids Say the F Sound?
What Age Should Kids Say the S Sound?
What Age Should Kids Say the L Sound?
What Age Should Kids Say the R Sound?
Working on more than one sound?
Chatter Batter started with my mom, Cindy Judd. She believed a child should feel loved, never tested, so she helped bring stories like these to life with the practice tucked inside. I’m Jed, a dad of seven, and I’ve been remastering these books so more families can read them together. One sound at a time, one story at a time.
This article is for general information, not a substitute for a speech-language evaluation. Every child grows at their own pace. If you’re wondering about your child’s speech or hearing, you don’t have to wait to ask your pediatrician or a speech-language pathologist.
Sources:
Crowe, K., & McLeod, S. (2020). Children’s English Consonant Acquisition in the United States: A Review. American Journal of Speech-Language Pathology, 29(4), 2155–2169. Ages in this article are when 90% of children say the sound clearly; the authors describe them as conservative.
American Speech-Language-Hearing Association. Speech Sound Disorders: Articulation and Phonology. Practice Portal.
American Academy of Pediatrics (2024). Literacy Promotion: An Essential Component of Primary Care Pediatric Practice.
Whitehurst, G. J. Dialogic reading. See the What Works Clearinghouse report.
A playful way to practice: Our free, ad-free kids’ arcade has a listening game called Sound Safari. Your child hears the “Th” sound, then taps the bushes whose words have it. It’s a fun extra for home, not a replacement for speech therapy.
