How to use
Pick your baby’s date of birth, and you’ll see the completed number of months as of today. If you need the age on another day, change the reference date. The result shows the completed months (the headline number) plus a more precise months-and-days breakdown, the total in weeks and days, the total number of days since birth, and the date of the next month milestone. It also lists upcoming milestones you’ll likely want to track — the next 3 months, plus 12, 18, and 24 months if they haven’t passed yet — each with its date.
How months are calculated
A month is complete once the same day-of-month as the birth date comes around again. If that month has no matching day, the last day of that month counts as the milestone. For example, a baby born on January 31 has no January 31 counterpart in February, so the baby turns 1 month old on February 28 in a common year, or February 29 in a leap year. This is the same calendar-month rule used by this site’s age and date calculators.
Corrected age for premature babies
Compared by actual age alone, a baby born before the due date can look behind other babies the same age. Corrected age compares development using the due date instead of the real birthday: it is the actual age in weeks minus (40 weeks minus the gestational age at birth). For example, a baby born at 32 weeks’ gestation is 8 weeks (2 months) early, so at 16 weeks (4 months) old, the corrected age is 8 weeks (2 months). Enter either the due date or the gestational age at birth to see the corrected age. HealthyChildren.org from the American Academy of Pediatrics (AAP) recommends using corrected age to track a premature baby’s development up to about 2 years old. This calculator’s result is informational only and does not replace a medical diagnosis or consultation.