Health Calculators
Corrected age calculator for premature babies.
Subtract the weeks your baby was born early from their actual age, the method the American Academy of Pediatrics describes. For information only, not medical advice.
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Enter your baby's date of birth and gestational age at birth.
Not medical advice. This tool only does arithmetic. Your baby's doctor decides how to use corrected age for your child.
How corrected age is calculated
The American Academy of Pediatrics (AAP) says to begin with your baby's actual age in weeks, the number of weeks since the date of birth, and subtract the number of weeks your baby was preterm. To find the weeks preterm, subtract gestational age at birth from 40. Example from the AAP: a baby born at 32 weeks was 8 weeks preterm; at 16 weeks since birth, the corrected age is 8 weeks (2 months).
The AAP states the rule in whole weeks. This calculator applies the same subtraction in days, so a birth at 32 weeks and 3 days is handled exactly. The AAP also says a pregnancy is now considered full term at 39 weeks, so births at 39 weeks or later get no correction here. The AAP says corrected age is used to gauge developmental goals during the first 2 years.
Corrected age is a way to think about developmental milestones. It is not a diagnosis, and it does not replace advice from your baby's doctor or nurse.
Source: American Academy of Pediatrics, HealthyChildren.org, Corrected Age for Preemies. Read 2026-09-29.