Corrected age calculator for prematurity
Enter date of birth, test date and gestational age at birth to get the corrected (adjusted) age for a preterm infant, in years; months; days. The tool subtracts the weeks born early so you can interpret development against term milestones.
Corrected age for prematurity
Corrected age subtracts the weeks born early from the term due date. Many clinicians stop correcting at 24 months (AAP) — some protocols use 36. Follow your own protocol; this is a labelled default, not a rule.
How we calculate this
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| Student | Date of birth | Test date | Age |
|---|
- Adjusted for prematurity — chronological age minus weeks early.
- Exact Y;M;D for both chronological and corrected age.
- Private — infant dates never leave your browser.
Corrected age for preterm infants
A baby born several weeks early has been in the world longer than their development would suggest, so comparing them to milestones normed on term-born infants can be misleading. Corrected age fixes this by counting from the due date instead of the birth date, giving a fairer picture of where the child is developmentally.
What corrected age is
Corrected age is the chronological age minus the number of weeks the baby was born premature — equivalently, the age measured from the term due date. Weeks premature is 40 − gestational age at birth in weeks, so a baby born at 30 weeks is 10 weeks early, and their corrected age is their chronological age minus those 10 weeks. A baby born at full term has no correction, and chronological and corrected age are the same.
When to use — and stop using — corrected age
The American Academy of Pediatrics (AAP) commonly describes correcting age through about 24 months of age; some protocols continue to 36 months for the most preterm infants. The tool uses a labelled default so you can see the assumption, but the cutoff is a clinical decision: follow your own program's protocol, and cite the AAP as the source when you document it. This is general guidance, not medical advice.
How to read the result
Open the Corrected-age drawer under the calculator and enter the gestational age at birth in weeks. The tool keeps the chronological age (date of birth to test date) on screen and shows the corrected age beside it in years; months; days, so you can record both figures. Adjust the test date to any assessment date to see the corrected age on that day.
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Corrected (adjusted) age — FAQ
How do I calculate corrected age for a premature baby?
Take the chronological age (date of birth to today or the assessment date) and subtract the number of weeks the baby was born early. Weeks premature is 40 minus the gestational age at birth, so a baby born at 32 weeks is 8 weeks early. Here you enter the date of birth, the test date and the gestational weeks in the Corrected-age drawer, and the tool does the subtraction for you and shows the result in years; months; days.
What is corrected (adjusted) age?
Corrected age — also called adjusted age — is a preterm infant's age counted from the original due date rather than the actual birth date. It answers "how old would this baby be if born on time?", which is the fairer basis for comparing growth and development against milestones normed on term infants.
How long do you use corrected age?
The American Academy of Pediatrics commonly describes correcting age through about 24 months (2 years); some programs and protocols continue to 36 months for very preterm infants. The right cutoff is the one in your own clinical protocol — this is guidance, not medical advice, so follow the policy your setting uses.
How do I calculate chronological age and corrected age?
Chronological age is simply the elapsed time from date of birth to the test date, in years; months; days. Corrected age is that same figure minus the weeks premature (40 minus gestational age at birth). The tool shows the chronological age and, once you enter gestational weeks in the drawer, the corrected age alongside it.
Corrected age vs chronological age — what's the difference?
Chronological age counts from the day the baby was actually born. Corrected age counts from the due date, removing the head start of an early birth. For a term baby the two are identical; for a preterm baby the corrected age is younger by the number of weeks born early, and it is the value used to interpret early development.