Speech & Communication

Toddler Replacing S and F Sounds with T and P

Medically reviewed by Dr. Emily Torres, PhD, CCC-SLP · Pediatric Speech-Language Pathologist

Content reviewed against published ASHA, AAP, NIH guidelines

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Speech and communication milestones vary widely, and worries about toddler replacing s and f sounds with t and p, here is what you need to know.

The short answer

Stopping is a phonological process where children replace continuous sounds like S, F, and Z with stop sounds like T, P, and D. For example, saying "tun" for "sun" or "pish" for "fish." Stopping is normal until around age 3 for most sounds and typically resolves without intervention. If it persists after age 3.5, speech therapy may help.

Key takeaways

  • Stopping is a phonological process where children replace continuous sounds like S, F, and Z with stop sounds like T, P, and D. For example, saying "tun" for "sun" or "pish" for "fish." Stopping is normal until around age 3 for most sounds and typically resolves without intervention. If it persists after age 3.5, speech therapy may help.
  • Usually normal when: Your toddler is under 3 and replaces F with P or S with T in most words
  • Call your doctor if: Your child was producing fricative sounds and has lost this ability
  • Varies by age — see the age-by-age breakdown below

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What Parents Should Know

According to ASHA, AAP, NIH guidelines, stopping is a phonological process where children replace continuous sounds like S, F, and Z with stop sounds like T, P, and D. For example, saying "tun" for "sun" or "pish" for "fish." Stopping is normal until around age 3 for most sounds and typically resolves without intervention. If it persists after age 3.5, speech therapy may help. At 12-18 months, stopping is very common and expected. Young children produce stop consonants (B, P, T, D) more easily than fricatives (S, F, Z, SH). Most early words will have stop sounds substituted for continuous sounds. It is generally considered normal when your toddler is under 3 and replaces F with P or S with T in most words. However, you should contact your pediatrician promptly if your child was producing fricative sounds and has lost this ability.

Sources: [1], [2], [3]

Normal vs. Concerning

Usually Normal
Worth Discussing
Your toddler is under 3 and replaces F with P or S with T in most words
Your child was producing fricative sounds and has lost this ability
Your toddler is beginning to produce some fricative sounds correctly while still stopping others
Your child is over 4 years with persistent stopping and multiple other speech sound errors
Your toddler produces F and S sounds in some words but not others, showing the process is resolving
Your child is over 3.5 years and still consistently stops all fricative sounds
Your toddler can produce fricative sounds when imitating you but not yet in spontaneous speech
Your child shows no progress in producing S, F, or Z sounds over the past several months

By Age

What to expect by age

12-18 months

Stopping is very common and expected. Young children produce stop consonants (B, P, T, D) more easily than fricatives (S, F, Z, SH). Most early words will have stop sounds substituted for continuous sounds.

18-24 months

Stopping remains a normal pattern. Some children begin producing F and S sounds in some contexts while still stopping in others. The emergence of fricatives varies from child to child.

24-36 months

Stopping of F, S, and Z sounds typically begins to resolve during this period. Your child may produce fricatives correctly in some words but not others. By age 3, most children have begun using F and S sounds correctly.

3-4 years

Stopping should be largely eliminated for F and S sounds by age 3.5. If your child is still consistently using stops for fricatives, speech therapy can help teach the correct production of these sounds.

4-5 years

Persistent stopping beyond age 4 is not expected and indicates a speech sound disorder that benefits from therapy. Most children respond well to treatment for this pattern.

What to Tell Your Pediatrician

  • Describe when you first noticed toddler replacing s and f sounds with t and p and how it has changed over time.
  • Note your baby's current age and which age-specific patterns you are seeing.
  • Mention if your child is over 3.5 years and still consistently stops all fricative sounds.
  • Mention if your child shows no progress in producing S, F, or Z sounds over the past several months.
  • Let your doctor know if you have noticed any related concerns, such as changes in feeding, sleep, or movement patterns.
  • Bring a list of any questions or observations you want to discuss at the appointment.

What Should You Do?

When to take action

Probably normal when...
  • Your toddler is under 3 and replaces F with P or S with T in most words
  • Your toddler is beginning to produce some fricative sounds correctly while still stopping others
  • Your toddler produces F and S sounds in some words but not others, showing the process is resolving
  • Your toddler can produce fricative sounds when imitating you but not yet in spontaneous speech
Mention at your next visit when...
  • Your child is over 3.5 years and still consistently stops all fricative sounds
  • Your child shows no progress in producing S, F, or Z sounds over the past several months
  • Your child's stopping pattern makes them very hard to understand
Act now when...
  • Your child was producing fricative sounds and has lost this ability
  • Your child is over 4 years with persistent stopping and multiple other speech sound errors

What You Can Do at Home

  • Keep track of when you notice toddler replacing s and f sounds with t and p — noting the time of day, duration, and any triggers can help your pediatrician.
  • Remember that your toddler is under 3 and replaces F with P or S with T in most words — this is generally within the range of normal.
  • At 12-18 months, focus on observation rather than intervention unless your pediatrician advises otherwise.
  • Talk, read, and sing to your baby frequently. Narrate daily activities to build language exposure.
  • While monitoring at home, seek immediate care if your child was producing fricative sounds and has lost this ability.

Toddler's Sound Pattern Errors Not Resolving

Phonological processes are normal sound pattern simplifications that young children use as they learn to talk. For example, saying "goggy" for "doggy" (fronting) or "poon" for "spoon" (cluster reduction). These patterns should gradually disappear by specific ages. If patterns persist beyond their expected resolution age, a speech-language evaluation is recommended.

Child Cannot Say the S Sound

The S sound is typically mastered between ages 3 and 5. Many young children substitute TH or T for S, which is normal developmental variation. A frontal lisp with S is common and often resolves by age 4.5. If S errors persist past age 5, or if your child has a lateral (slushy) lisp, a speech evaluation is recommended.

Toddler Has Multiple Speech Sound Errors

A speech sound disorder involves difficulty producing speech sounds correctly, making a child harder to understand than expected for their age. While individual sound errors are common in toddlers, having many sound errors that significantly reduce intelligibility may indicate a speech sound disorder that benefits from speech therapy. Early evaluation and treatment lead to the best outcomes.

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General guide on when to call the pediatrician, visit urgent care, or go to the ER.

Frequently asked questions

Is toddler replacing s and f sounds with t and p normal?
Stopping is a phonological process where children replace continuous sounds like S, F, and Z with stop sounds like T, P, and D. For example, saying "tun" for "sun" or "pish" for "fish." Stopping is normal until around age 3 for most sounds and typically resolves without intervention. If it persists after age 3.5, speech therapy may help.
When should I call the doctor about toddler replacing s and f sounds with t and p?
Your child was producing fricative sounds and has lost this ability Your child is over 4 years with persistent stopping and multiple other speech sound errors
When is toddler replacing s and f sounds with t and p normal?
Your toddler is under 3 and replaces F with P or S with T in most words Your toddler is beginning to produce some fricative sounds correctly while still stopping others Your toddler produces F and S sounds in some words but not others, showing the process is resolving
What causes toddler replacing s and f sounds with t and p?
Stopping is a phonological process where children replace continuous sounds like S, F, and Z with stop sounds like T, P, and D. For example, saying "tun" for "sun" or "pish" for "fish." Stopping is normal until around age 3 for most sounds and typically resolves without intervention. If it persists after age 3.5, speech therapy may help. Common explanations include: Your toddler is under 3 and replaces F with P or S with T in most words. Your toddler is beginning to produce some fricative sounds correctly while still stopping others.
What should I mention to my pediatrician about toddler replacing s and f sounds with t and p?
You should mention toddler replacing s and f sounds with t and p at your next visit if: Your child is over 3.5 years and still consistently stops all fricative sounds. Your child shows no progress in producing S, F, or Z sounds over the past several months. Your child's stopping pattern makes them very hard to understand.
Is toddler replacing s and f sounds with t and p normal at 12-18 months?
Stopping is very common and expected. Young children produce stop consonants (B, P, T, D) more easily than fricatives (S, F, Z, SH). Most early words will have stop sounds substituted for continuous sounds.
Is toddler replacing s and f sounds with t and p normal at 18-24 months?
Stopping remains a normal pattern. Some children begin producing F and S sounds in some contexts while still stopping in others. The emergence of fricatives varies from child to child.
Should I go to the ER for toddler replacing s and f sounds with t and p?
Seek emergency care if your child was producing fricative sounds and has lost this ability, or if your child is over 4 years with persistent stopping and multiple other speech sound errors. When in doubt, call your pediatrician's after-hours line for guidance.
Does toddler replacing s and f sounds with t and p go away on its own?
In many cases, toddler replacing s and f sounds with t and p resolves on its own, especially when your toddler is under 3 and replaces F with P or S with T in most words. By 4-5 years, persistent stopping beyond age 4 is not expected and indicates a speech sound disorder that benefits from therapy. Most children respond well to treatment for this pattern.
ASHAAAPNIH

References

  1. [1]American Speech-Language-Hearing Association. Speech Sound Disorders: Articulation and Phonology. ASHA
  2. [2]American Academy of Pediatrics. Speech and Language Development. HealthyChildren.org. AAP
  3. [3]National Institute on Deafness and Other Communication Disorders. Speech and Language Developmental Milestones. NIH

Doctor Visit Checklist

Bring this checklist to your next pediatrician visit to discuss Toddler Replacing S and F Sounds with T and P.

Things to mention

  • Describe when you first noticed toddler replacing s and f sounds with t and p and how it has changed over time.
  • Note your baby's current age and which age-specific patterns you are seeing.
  • Mention if your child is over 3.5 years and still consistently stops all fricative sounds.
  • Mention if your child shows no progress in producing S, F, or Z sounds over the past several months.
  • Let your doctor know if you have noticed any related concerns, such as changes in feeding, sleep, or movement patterns.
  • Bring a list of any questions or observations you want to discuss at the appointment.

Observations to share

  • Your child is over 3.5 years and still consistently stops all fricative sounds
  • Your child shows no progress in producing S, F, or Z sounds over the past several months
  • Your child's stopping pattern makes them very hard to understand

Urgent signs to report immediately

  • Your child was producing fricative sounds and has lost this ability
  • Your child is over 4 years with persistent stopping and multiple other speech sound errors

My notes

From ismybabyalright.com — free, evidence-based baby health guides

All content follows our editorial policy and is reviewed against published clinical guidelines.

2,705 evidence-based guides6 authoritative medical sources5 medical advisory board members

Related Resources

Milestone ChecklistsEarly Intervention DirectoryDevelopmental ActivitiesBaby Sign Language GuideBaby Tracker

Bottom line

Most cases of toddler replacing s and f sounds with t and p are normal. Talk to your pediatrician if your child was producing fricative sounds and has lost this ability.

Trust your instincts. If something feels wrong, reach out to your pediatrician. Worrying about your baby means you care — that is a good thing.

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Related Speech Concerns

Toddler's Sound Pattern Errors Not Resolving

Phonological processes are normal sound pattern simplifications that young children use as they learn to talk. For example, saying "goggy" for "doggy" (fronting) or "poon" for "spoon" (cluster reduction). These patterns should gradually disappear by specific ages. If patterns persist beyond their expected resolution age, a speech-language evaluation is recommended.

Child Cannot Say the S Sound

The S sound is typically mastered between ages 3 and 5. Many young children substitute TH or T for S, which is normal developmental variation. A frontal lisp with S is common and often resolves by age 4.5. If S errors persist past age 5, or if your child has a lateral (slushy) lisp, a speech evaluation is recommended.

Toddler Has Multiple Speech Sound Errors

A speech sound disorder involves difficulty producing speech sounds correctly, making a child harder to understand than expected for their age. While individual sound errors are common in toddlers, having many sound errors that significantly reduce intelligibility may indicate a speech sound disorder that benefits from speech therapy. Early evaluation and treatment lead to the best outcomes.

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