Premature Baby Age Calculator – Adjusted Age for Preemies

For infants born prematurely, many developmental assessments use adjusted (corrected) age until 2 years: age from the due date, not the birth date. Our calculator supports both: use the due date as "Start Date" and the test or visit date as "End Date" to get adjusted age in years, months, and days.

For children over 2, most protocols use chronological age (birth date). Enter birth date and test date in the same tool to get chronological age. One free calculator for both adjusted and chronological age.

No signup required. Used by NICU follow-up, early intervention, and developmental screening.

Adjusted vs Chronological Age for Preemies

Infants born before full term are often developmentally compared using adjusted (corrected) age—age from the due date rather than the birth date—until around 2 years. This corrects for the time the baby was not yet born and helps avoid over-referral for delay when a preemie is simply younger in terms of expected development. Many guidelines recommend using adjusted age for developmental screening and some assessments in the first two years of life.

Our premature baby age calculator is the same tool as our main chronological age calculator: to get adjusted age, use the due date as Start Date and the visit or test date as End Date. To get chronological age, use birth date as Start Date. The result is always in years, months, and days. For more on when to use adjusted age, read our premature baby adjusted age guide.

Quick reference:

• Adjusted age (under 2): Start Date = due date, End Date = visit or test date
• Chronological age (any age): Start Date = birth date, End Date = test or visit date
• Used by NICU follow-up, early intervention, and developmental screening

Open the calculator below and enter the appropriate dates for adjusted or chronological age.