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Stages I - V+Free in-browser calculator

Brown's Stages Lookup.

The classic Brown (1973) framework for early grammatical development, rendered as an interactive chart. Type an MLU or a child age and jump to the matching stage, milestones, and example utterances.

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Validated2026-04-06
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Look up a Brown's stage

Enter an MLU-morphemes value or a child age in months. The tool maps the input to the matching Brown's stage and shows the milestones you should be hearing at that stage.

Typical range 1.0 - 5.5 for children under 6.

All Brown's stages

Single-word and two-word combinations expressing semantic relations.

Grammatical milestones

  • Single-word utterances
  • Two-word combinations (agent-action, action-object, possessor-possession)
  • Semantic relations without grammatical morphemes

Example utterances

  • dog
  • more milk
  • mommy go
  • big truck
  • baby eat

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When to use

  • Placing a child in Brown's stages I-V+ based on computed MLU-morphemes
  • Planning therapy targets by selecting morphemes from the next stage above the child
  • Teaching SLP graduate students the framework for early grammatical development
  • Writing the developmental framing section of an evaluation report
  • Quickly checking which morphemes should be emerging for a child's approximate age
  • Comparing expected grammatical milestones against observed utterances in a language sample

Do not use for

  • Diagnosing language disorder from stage alone — Brown's stages are descriptive, not diagnostic
  • Assessing bilingual children with the English Brown's stages without collecting a sample in both languages
  • Interpreting school-age grammar — above Stage V+ MLU is less sensitive, shift to narrative measures
  • Assuming the age ranges are hard cut-offs — Brown's longitudinal data is from three children and age bands are approximate

Brown's stages describe, age norms grade

Brown's stages tell you *what* grammatical structures a child is producing. SUGAR and Rice norms tell you *whether* that is on schedule for age. Always pair the two — reporting a Brown's stage without an age comparison is incomplete.

Target the next stage, not the current stage

A child in Stage II already has present progressive -ing and prepositions *in* and *on*. Do not target those. Select morphemes from Stage III (irregular past, possessive -s, negation) as emerging therapy goals. Stay in the child's zone of proximal development.

The order is more reliable than the age

Brown's (1973) order of acquisition replicates robustly across children. The age ranges come from three children (Adam, Eve, Sarah) and are approximate. Trust the order, not the ages.

Stage V+ requires 90% mastery in obligatory contexts

A child is not in Stage V+ the first time they produce a contracted auxiliary. Brown defined mastery as correct use in 90% of obligatory contexts across three consecutive samples. Use that bar before declaring morpheme mastery.

Above MLU 5, stage becomes less informative

Brown's framework peaks at Stage V+ (MLU 4.5+). For school-age children, MLU plateaus and clinicians should shift to clausal density, subordination index, narrative-level metrics, and written language measures for meaningful progress tracking.

1

Method

Stage boundaries are taken from Brown (1973) *A First Language: The Early Stages* and codified in the shared SLP normative library (src/lib/slp/norms.ts). MLU-to-stage mapping uses Brown's original MLU ranges: Stage I (1.0-1.99), Stage II (2.0-2.49), Stage III (2.5-2.99), Stage IV (3.0-3.74), Stage V (3.75-4.49), Stage V+ (>=4.5). Age ranges are Brown's approximate age-of-emergence bands and should be interpreted as developmental guides, not diagnostic cut-offs.

2

Validated

Last validated 2026-04-06. Calculations are designed for planning and documentation support; verify procurement decisions against manufacturer specifications or institutional SOPs.

3

How to cite

How to Cite

ConductScience Brown's Stages Lookup (v1.0). ConductScience, Inc. 2026. Available at: https://conductscience.com/tools/browns-stages-lookup

Brown R. A First Language: The Early Stages. Harvard University Press; 1973.

Miller JF, Chapman RS. The relation between age and mean length of utterance in morphemes. Journal of Speech and Hearing Research. 1981;24(2):154-161. doi:10.1044/jshr.2402.154

Rice ML, Smolik F, Perpich D, Thompson T, Rytting N, Blossom M. Mean length of utterance levels in 6-month intervals for children 3 to 9 years with and without language impairments. JSLHR. 2010;53(2):333-349. doi:10.1044/1092-4388(2009/08-0183)

Pavelko SL, Owens RE. Sampling Utterances and Grammatical Analysis Revised (SUGAR): New normative values for language sample analysis measures. LSHSS. 2017;48(3):197-215. doi:10.1044/2017_LSHSS-17-0022

What Are Brown's Stages?

Brown's stages are a developmental framework introduced by Roger Brown in his 1973 book *A First Language: The Early Stages*. Brown partitioned early grammatical development into five stages based on Mean Length of Utterance (MLU) in morphemes, with each stage marked by the emergence of specific grammatical structures.

Why MLU? Brown argued that a child's grammatical maturity is captured more faithfully by MLU than by chronological age, because children vary widely in when they acquire language. A 30-month-old and a 36-month-old can sit in the same Brown stage if they produce utterances of the same average length. MLU is the single best predictor of which grammatical structures a child has under productive control.
Descriptive, not normative. Brown's stages describe *what* happens in early grammatical development, not whether a given child's progress is typical for age. To decide whether a child's MLU is age-appropriate, pair Brown's stages with SUGAR (Pavelko & Owens 2017) or Rice et al. (2010) age norms.

How to Use This Tool

The lookup tool lets you find a Brown's stage three ways:

  • By MLU: type a Mean Length of Utterance in morphemes to see which stage the child falls into, the age range Brown associated with the stage, and the morphemes and structures that should be emerging.
  • By age: enter the child's age in months to see the stage most typically developing children are in at that age. Use this as a screening check, not a diagnostic cut-off.
  • Browse all stages: scroll through the full chart to see every stage side-by-side with MLU range, age range, key structures, and example utterances.
Next step. Once you know the child's stage, use the stage's morpheme list to plan therapy targets: pick one or two morphemes from the *next* stage above as SMART goals for expressive language therapy.

Brown's 14 Morphemes — Order of Acquisition

Brown (1973) documented the order in which 14 grammatical morphemes are mastered by typically developing children. The order is remarkably stable across children, though the *age* at which each morpheme is mastered varies. Mastery is defined as correct use in 90% of obligatory contexts across three consecutive language samples.

1. Present progressive -ing (mommy running) — ~19-28 mo 2. **Preposition *in* (ball in box) — ~27-30 mo 3. Preposition *on* (book on table) — ~27-30 mo 4. Regular plural -s (two dogs) — ~27-33 mo 5. Irregular past tense (went, ate) — ~25-46 mo 6. Possessive -s (daddy's hat) — ~26-40 mo 7. Uncontractible copula (there it is) — ~27-39 mo 8. Articles (a, the) — ~28-46 mo 9. Regular past -ed (walked, jumped) — ~26-48 mo 10. Regular third-person singular -s (she runs) — ~26-46 mo 11. Irregular third-person singular (does, has) — ~28-50 mo 12. Uncontractible auxiliary (is he running?) — ~29-48 mo 13. Contractible copula (he's happy) — ~29-49 mo 14. Contractible auxiliary** (he's running) — ~30-50 mo

For therapy planning, target morphemes the child is on the cusp of acquiring — typically one or two notches ahead of their current productive control.

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Next steps

Protocol

MLU Calculator — compute MLU-morphemes from a transcript

Reference protocol for the next planning step.

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SUGAR Norms Lookup — age-matched reference values

Reference protocol for the next planning step.

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Lexical Diversity Calculator — TTR and NDW

Reference protocol for the next planning step.

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PGU Calculator — percentage of grammatical utterances

Reference protocol for the next planning step.

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