Collect a sample of the child’s speech, typically around 50-100 utterances. Count the number of morphemes in each utterance. Morphemes include words, prefixes, and suffixes. Divide the total number of morphemes by the total number of utterances.
For example, if a child produces 150 morphemes in 50 utterances, the MLU would be 150 divided by 50, which equals 3.0.
