Utterance length and language sample calculator

How to use this tool

Use this Mean Length of Utterance (MLU) calculator to summarize language sample utterance length in words (MLUw) and clinician-scored morphemes (MLUm).

• Describe the language sample context, language variety, partner condition and morpheme convention.
• Enter complete intelligible utterances as the denominator, along with total words and optional morphemes.
• Select a compatible series and review MLU ratios and excluded utterance counts before exporting.

Fictional example and how to read the result

Fictional example: 50 complete utterances with 175 words yields an MLUw of 3.50 words per utterance. Four unintelligible utterances are excluded from the ratio.

These arithmetic ratios describe entered language samples. They provide no developmental age norms, automated grammatical analysis or clinical diagnoses.

Measure language sample utterance length with consistent segmentation

Enter utterance, word and morpheme counts scored from an authentic language sample by a qualified speech-language professional. Mean length of utterance in words (MLUw) divides total words by complete intelligible utterances. Mean length of utterance in morphemes (MLUm) divides total morphemes by complete intelligible utterances.

Unintelligible, abandoned or singing utterances are excluded from the MLU denominator under standard clinical rules, but must be reported so sample quality remains transparent.

Morpheme segmentation conventions vary by language, age and theoretical framework. Never pool samples across different languages or segmentation conventions. This tool computes arithmetic ratios; it does not transcribe audio, apply developmental norms or diagnose developmental language disorder (DLD).

• State the elicitation context, language and morpheme counting convention for each series.
• Enter complete intelligible utterances as the denominator for word and morpheme counts.
• Record excluded or unintelligible utterances in their own column to retain sample size.
• Total morphemes must be at least total words when morphemes are scored.

What to enter in each field

• Measure to graph: Choose whether to graph Mean Length of Utterance in words (MLUw) or morphemes (MLUm).
• Chart series label (optional): Optional series label to graph. Leave blank to display the first compatible language sample series.
• Observation date: Use the date of this language sample. Imported dates must be real YYYY-MM-DD dates.
• Series label: Label repeated comparable language samples anonymously. Keep context and convention consistent.
• Language and variety: State the sample language and variety, such as English. Different languages are never pooled.
• Sampling context and partner: Describe the conversational or play setting and communication partner condition anonymously.
• Segmentation and morpheme rule: Record the segmentation and morpheme counting rule, such as Brown rules or C-unit analysis.
• Complete intelligible utterances: Whole count of fully intelligible, non-abandoned utterances used for MLU calculation.
• Excluded / unintelligible utterances: Optional count of unintelligible or abandoned utterances excluded from the MLU denominator.
• Total words in complete utterances: Total word count across all complete intelligible utterances in this language sample.
• Total morphemes (optional): Optional total bound and free morpheme count across complete utterances under the declared rule.
• Longest utterance in words (optional): Optional length of the longest utterance in words within this language sample.

Original fictional example and data fields

Use the editable blank CSV or local import to collect your own de-identified entries. The example below is fictional.

Swipe or scroll sideways to view all table columns.

Professional sources and permissions

Original worksheets and arithmetic support recording and planning. Follow the official publisher routes for standardized instruments.

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