What is corrected gestational age?

Corrected gestational age (CGA), also called adjusted age, is the age a premature infant would be if they had been born at full term (40 weeks). It is calculated by subtracting the number of weeks premature from the baby's chronological (calendar) age. For example, a baby born at 28 weeks (12 weeks early) who is 6 months old chronologically has a corrected age of about 3 months.

Why use corrected age instead of chronological age?

Premature infants need extra time to develop compared to full-term babies. Using chronological age for developmental milestone screening would unfairly flag normal preterm development as delayed. Corrected age accounts for the shortened time in the womb and gives a more accurate picture of where the infant is developmentally.

Until what age should corrected age be used?

Most guidelines recommend using corrected age for developmental assessments until 2 years of age. For very preterm infants (born before 28 weeks), some specialists continue correction up to 3 years. After that, most children have caught up sufficiently that correction is no longer clinically meaningful.

What is full-term gestational age?

A full-term pregnancy is 40 weeks from the last menstrual period. A baby born before 37 weeks is considered preterm. This calculator uses 40 weeks as the baseline for computing the prematurity offset.

My baby's corrected age is negative — what does that mean?

A negative corrected age means the baby has not yet reached their original due date. For example, a baby born at 30 weeks who is only 4 weeks old chronologically is still 6 weeks before their due date. The calculator displays 0 in this case, indicating the baby is still in the pre-term window.

Corrected Gestational Age Calculator

Name: Corrected Gestational Age Calculator
Availability: InStock
Author: Nham Vu

Enter your premature infant's date of birth, gestational age at birth, and today's date to get the corrected (adjusted) age in weeks or months.

Baby Information

Date of Birth

Gestational Age at Birth

22–41 weeks

0–6 days (optional)

Assessment Date Defaults to today

Enter birth information on the left to calculate corrected age.

Summary

Enter your premature infant's date of birth, gestational age at birth, and today's date to get the corrected (adjusted) age in weeks or months.

How it works

The tool computes chronological age as the number of days from birth to today, then subtracts the prematurity offset — the difference between 40 weeks (full term) and the gestational age at birth in days. The result is converted to weeks and months for display. Corrected age is capped at zero if the baby has not yet reached the original due date.

Use cases

Determine the corrected age to use when assessing developmental milestones in a preterm infant.
Calculate how many weeks early a baby was born and what their adjusted age is today.
Track a premature infant's progress relative to their original due date.
Compare chronological and corrected ages at a pediatric follow-up appointment.
Understand when a preterm baby is expected to "catch up" to full-term peers.

Frequently Asked Questions

Last updated: 2026-07-22 · Reviewed by Nham Vu