Corrected Age for Preemies
v1.0A one-page guide for parents of premature babies — print it and bring it to your next pediatric visit.
What is corrected age?
Corrected age (also called adjusted age) is the age your premature baby would be if they had been born on their due date instead of their actual birth date. It answers the question: "How old would my baby be if they had arrived on time?"
Babies miss out on growth that would have happened in the womb when they arrive early. Corrected age accounts for that missed time, so you compare your baby's development against realistic expectations — not against full-term babies born on the same day.
The formula
Corrected age = today's date − due date
Equivalently: take your baby's actual (chronological) age and subtract how many weeks early they were born.
Example: born January 1 at 8.4 weeks early (due date March 1). On June 1 the chronological age is 5 months, but the corrected age is 3 months. For milestones, compare against 3-month expectations.
When to use which age
Use corrected age for
- Developmental milestones (sitting, crawling, walking)
- Speech and language expectations
- Growth tracking discussions
- Early intervention evaluations
Always use actual age for
- Vaccination schedules
- Medication dosing
- Legal documents and records
Per the American Academy of Pediatrics' HealthyChildren.org guidance linked in the sources below.
How long should you correct?
Most providers use corrected age until your child's second birthday. By then, most preterm children have caught up with their full-term peers. For babies born very early (before 28 weeks), some providers adjust a little longer — ask your pediatrician what they recommend for your child.
Calculate it instantly
Our adjusted (corrected) age calculator shows chronological and corrected age side by side, the weeks-premature figure, the date correction typically stops, and a printable summary — all computed privately in your browser.
Disclaimer: This calculator is an educational tool, not medical advice. Always follow your pediatrician's guidance for your child's health, development, vaccinations, and medication.