This is a great question and one of the most common questions parents ask. Below is a fantastic visual that was created and can be found here: McLeod, S. (2012). Summary of 250 cross-linguistic studies of speech acquisition. Bathurst, NSW, Australia: Charles Sturt University. Retrieved 12/6/2022 from http://www.csu.edu.au/.../multilingual.../speech-acquisition
It is based on a systematic review published in 2020 in a peer-reviewed journal. It’s an open-access article for those of you interested in digging deeper: Crowe, K., & McLeod, S. (2020). Children's English consonant acquisition in the United States: A review. American Journal of Speech-Language Pathology. https://doi.org/10.1044/2020_AJSLP-19-00168 Basically, 90% of English-speaking children in the United States should be able to say the sounds listed under their age plus those under the ages below them.
For example, by age 3 years, most children (90%) should be able to say the following sounds:
/t/ as in “toy,”
/k/ as in “cat,”
/g/ as in “go,”
/ng/ like at the end of the word “running,”
/f/ as in “foot,” and
/y/ as in “yes.”
And, they should also be able to produce those listed under age 2:
/p/ as in “papa,”
/b/ as in “boy,”
/d/ as “dog,”
/m/ as in “mine,”
/n/ as in “no,”
/h/ as in “hat,” and
/w/ as in “water.”
If you have concerns about your child’s articulation development, speak with a speech-language pathologist (SLP) at your child’s school, through a local hospital, or with one at a local private practice. While articulation therapy can be successful at any age, it is often easier and more efficient to address difficulties sooner before habits become second nature.