Premature Baby Corrected Age Calculator

If your baby was premature, he or she has two ages for the first few years: Chronological age, which is how old your baby is from date of birth; And, corrected age, which is how old your baby would be if born on his or her due date rather than prematurely. Corrected date is often used when assessing growth and developmental skills. This calculator shows your baby's chronological age and adjusted age.

Adjust Your Premature Baby's Age

*If necessary, check with your baby's doctor to determine your baby's gestational age (that is, the week number when your baby was born), and what your doctor considers a full term pregnancy. General information on full term, pre-term and post-term pregnancy below.

Related calculators: Calculate your pregnancy length which shows how many weeks you were pregnant.

Age Adjustment Calculation

To adjust your baby's age, the number of weeks your baby is premature is subtracted from your baby's chronological age in weeks. For example, if your baby was 5 weeks premature (ie. born at week 35 based on full term of 40 weeks), and it's been 20 weeks since your baby was born, your baby's corrected age is 15 weeks old (20 - 5 = 15).

What is full term pregnancy?

Until recently, babies born between 37 weeks and 42 weeks were considered full-term, with 40 weeks from last menstrual period (LMP) being the average. However, in 2013, The American College of Obstetricians and Gynecologists (ACOG) and the Society for Maternal-Fetal Medicine (SMFM) introduced new definitions for term pregnancies, as shown in the table below. Re-defining full term pregnancy is being done "to improve newborn outcomes and expand efforts to prevent non-medically indicated deliveries before 39 weeks of gestation." [More at] Also find out more about full term and 39 weeks at March of Dimes.

From Pregnancy WeekTo Pregnancy Week
Early Term37 Weeks, 0 Days38 Weeks, 6 Days
Full Term39 Weeks, 0 Days40 Weeks, 6 Days
Late Term41 Weeks, 0 Days41 Weeks, 6 Days
Post Term42 Weeks, 0 DaysBeyond 42 Weeks

Note that the definition of pre-term has not changed, and refers to babies born prior to 37 weeks and 0 days.

Disclaimer: All information provided on this calculator, including corrected age, is for informational purposes only and should not be relied on for any medical or other decisions. It is not intended as a substitute for professional medical advice. You should always consult with your pediatrician and/or your child's healthcare provider for answers to your and your child's particular medical situation.