Corrected Age Calculator for Premature Babies
For a baby born before 37 weeks, chronological age alone isn’t the number pediatricians and early intervention teams use for growth and developmental tracking. They use corrected (adjusted) age instead. This calculator computes both at once, from the actual birth date and gestational age at birth.
Chronological Age vs. Corrected (Adjusted) Age
Chronological age is time since actual birth. Corrected age subtracts how early the baby arrived, so development gets compared to full-term peers fairly. The formula:
Adjustment for prematurity = 40 weeks (full term) − gestational age at birth
Corrected age = Chronological age − Adjustment for prematurity
This calculator runs both numbers at once from the same three inputs, with no manual subtraction needed.
Who Uses Corrected Age
- ASQ-3 and ASQ:SE-2 screening: form selection is based on corrected age, not chronological age, for preemies under 24 months.
- Bayley-4 and other developmental assessments in NICU follow-up clinics.
- Pediatric growth chart plotting: most guidance recommends using corrected age through 2 years, since most premature infants catch up to full-term peers by that point.
What’s the difference between this and entering a due date on your other calculators?
This one takes the actual birth date and gestational age directly and shows both the chronological and corrected age side by side, so you don’t need to calculate a due date yourself first.
Until what age is corrected age used?
Most pediatric guidance uses corrected age for growth and developmental tracking through 2 years of age, since most premature infants catch up to full-term peers by that point.
Is corrected age the same as gestational age?
No. Gestational age is time spent in the womb before birth. Corrected age is chronological age minus the number of weeks a baby was born early. See what chronological age is for how the two compare to other age types.