About the Adjusted Age Calculator
Babies born early are, in a developmental sense, younger than their birthday suggests. Adjusted age (also called corrected age) accounts for prematurity by measuring age from the original due date instead of the birth date. It is the standard way pediatric teams track a preterm infant's growth and developmental milestones during roughly the first two years.
The formula
A full-term pregnancy is counted as 40 weeks. The number of weeks a baby was born early is therefore 40 weeks minus the gestational age at birth. Subtract that from the child's chronological age (time since birth) to get the adjusted age:
- Weeks born early = 40 weeks − gestational age at birth.
- Adjusted age = chronological age − weeks born early.
Example: a baby born at 32 weeks was 8 weeks early. At a chronological age of 20 weeks, the adjusted age is 20 − 8 = 12 weeks, about 2.8 months. Growth and milestones are read against 12 weeks, not 20.
How to get accurate results
- Use the gestational age recorded at delivery, expressed as completed weeks plus extra days (for example, 32 weeks and 3 days).
- Enter chronological age as the time elapsed since the birth date, not since the due date.
- The tool corrects relative to a 40-week due date; correction is most meaningful for babies born before 37 weeks.
Putting the result in context
Adjusted age is the fair yardstick for a preterm baby. A 12-week-old born two months early is fairly compared with a full-term 4-week-old, not another 12-week-old. Correction is commonly applied until about 2 years of age, after which the developmental gap usually narrows and chronological age is used again.
When to consult a professional
This calculator is an estimate for tracking milestones and reading growth charts; it does not diagnose developmental delay. Discuss any concerns about your child's growth or development with a pediatrician or licensed healthcare provider, who can interpret adjusted age alongside your child's full history.