Baby Age Calculator

Enter your baby birth date to see their age in weeks, months, and days. If your baby was born early, add the original due date and this tool also shows corrected (adjusted) age, which providers use to track a preemie growth and milestones until about age 2.

Free tool Tools Updated June 2026

Actual age vs corrected age

Actual (chronological) age counts from your baby birth date and is what you use for most things day to day. Well-child visits, vaccine timing, and milestone charts are organized by age in months, so this tool shows weeks, calendar months, and total days to match whichever a chart uses.

Corrected age, also called adjusted age, applies to babies born premature. It subtracts the number of weeks early (the gap between the birth date and the original due date) so development is judged against where the baby would be if born at term. Providers track growth and milestones by corrected age, usually until about 2 years old. Enter the due date above to see it.

Related questions

How do I calculate corrected age?
Subtract the number of weeks your baby was born early from their actual age. This tool does it for you: enter the birth date and the original due date, and it counts corrected age from the due date. It is used for tracking development, usually until about age 2.
What is the difference between corrected and actual age?
Actual age counts from the birth date; corrected (adjusted) age counts from the original due date for babies born early. A baby born 8 weeks early has a corrected age 8 weeks behind their actual age, which is the fairer way to judge milestones.
When are the well-baby checkups?
Typical AAP well-child visits fall at 1, 2, 4, 6, 9, 12, 15, 18, 24, and 30 months, then yearly. Knowing your baby age in months helps you keep them on schedule; for preemies, ask whether to use actual or corrected age.

Sources & further reading

  1. AAP HealthyChildren — Preemie Milestones (Corrected Age)
  2. AAP HealthyChildren — Well-Child Visit Schedule
  3. CDC — Developmental Milestones (Learn the Signs. Act Early.)

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This tool gives general estimates for education only and is not medical advice or a diagnosis. For a baby born premature, use corrected age for milestones until about age 2, and follow your provider guidance. For your own care, contact your healthcare provider.