Age in Months Calculator
Enter a date of birth to find the total number of completed months of age, with days left over.
Your calculation is performed in your browser.How it works
The calculator counts full completed calendar months between the date of birth and the calculation date, using each month's real length rather than a flat 30-day assumption.
Formula & methodology
Completed months come from calendar subtraction, so they respect real month lengths. Leftover days are reported separately. A decimal approximation is shown for comparison only.
Completed months
Total months = (Years × 12) + MonthsLeftover days
Remaining days = Days from the calendar subtractionApproximation
Approx. months = Total days ÷ 30.44What each term means
- Years, Months, Days
- The result of subtracting the date of birth from the calculation date on the calendar.
Worked example
A baby born on January 10, 2026 is 8 months and 3 days old on September 13, 2026 — 8 completed months.
Common uses
- —Tracking a baby or toddler’s age in months for growth charts and vaccination schedules.
- —Answering “how many months old is my baby today” for milestone tracking apps or baby books.
- —Converting a birth date into a precise months-and-days figure for pediatric appointments.
Important notes
- —Because months vary from 28 to 31 days, "total completed months" is always based on real calendar months, never a flat 30-day estimate.