Convert a premature baby’s chronological age into adjusted (corrected) age from gestational age at birth.
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Adjusted age (weeks)
How to use this tool
In completed weeks, as recorded at delivery (for example 32 weeks).
The baby's actual age since birth, in weeks.
Chronological age minus weeks premature — the age used for milestones.
Compare development and growth-chart position against adjusted age, as the paediatrician directs.
Formula & worked example
A baby born at 32 weeks who is now 52 weeks old chronologically has an adjusted age of 44 weeks (52 − 8 weeks premature) — about 10 months.
Limitations — read this before you rely on it
Adjusted age is a developmental convention, not a medical measurement, and its use varies (often to age 2, sometimes longer for very premature babies). It does not account for medical complications or individual development. This tool is not medical advice — follow the paediatrician's guidance for your child.
Frequently asked questions
The age a premature baby would be if born at term: chronological age minus the number of weeks born early.
Milestones and growth charts are based on development from conception, so a premature baby is fairly compared against adjusted, not chronological, age.
Commonly until age 2; for very premature babies some clinicians continue to age 3 for developmental assessments.
Weeks premature is zero, so adjusted age equals chronological age.
Vaccinations generally follow chronological age, while developmental expectations follow adjusted age — always confirm with the paediatrician.