Corrected Age Calculator (Preemie)

Corrected age (also called adjusted age) is a preemie's age based on the original due date instead of the actual birth date. You take the chronological age, the time since birth, and subtract the number of weeks the baby was born early. It estimates where the baby would be developmentally if the pregnancy had reached full term, so growth and milestones can be judged fairly.

First find the weeks of prematurity: 40 weeks (the full-term reference) minus the gestational age at birth. Then subtract those weeks from the chronological age. For example, a baby born at 32 weeks is 8 weeks early, so a 13-week-old has a corrected age of 5 weeks. This calculator runs the same math from either the gestational age at birth or the original due date.

Either one works, and both give the same corrected age. If you know the original due date, the calculator measures the time from that date to the date you pick. If you know the gestational age at birth (for example 32 weeks and 3 days), it subtracts that from 40 weeks to find how early the baby arrived. Use whichever number you have on hand.

Most clinicians correct a premature baby's age until about 2 years, and some continue to 3 years for very early births. After that, the gap between corrected and chronological age usually stops mattering for development and milestone tracking. Babies born before 37 weeks of gestation are the ones who typically need correction.

Yes. If the date you choose is before the baby's original due date, the corrected age is negative, which means the baby has not yet reached the point of a full-term birth. The calculator shows this as a number of weeks before the due date. Clinical teams often track these early weeks as postmenstrual age, which adds the gestational age at birth to the chronological age.

No. This tool is for education and general information only, and it is not a substitute for professional medical advice. Always rely on your pediatrician or neonatologist for decisions about your baby's growth, milestones, and care.