Baby Age Calculator

A baby's age changes fast, and in the first couple of years it is measured in months and days rather than whole years. This calculator gives your baby's exact age from their date of birth: the completed years and months, the extra days on top, and the total number of days they have been alive.

Those small units matter more for an infant than for anyone else. Health visits, growth charts, feeding and sleep guidance, and developmental milestones are all organised by age in months, so knowing precisely how many months and days old your baby is helps you line them up with the right stage. It is also lovely to mark the little milestones — the first hundred days, the half-year point — that fall between birthdays.

The calculation uses the real length of each month rather than a flat thirty days, so the month count is accurate as your baby moves across months of different lengths. It handles leap years correctly too, which matters for babies born on or near 29 February. Alongside the months-and-days breakdown, it shows the total days old, which many parents like to track in the early weeks.

To use it, choose your baby's date of birth and press Calculate age. Their exact age appears instantly, computed privately in your browser with nothing sent anywhere. A future date is rejected with a clear message.

For an older child or yourself, the standard age calculator returns the same breakdown, and the how many days old am I page focuses on the running day count.

If your baby was born early, enter the weeks born early and the calculator also shows the corrected age, which is the age counted from the due date instead of the birth date. For a baby born 8 weeks early, corrected age is 8 weeks younger than chronological age. Paediatricians commonly use corrected age to judge growth and milestones until around 2 years, then switch to chronological age. Leave it at 0 for a baby born at full term, and follow your own doctor's advice about which age to use.

Your baby's age is the completed years and months from their date of birth to today, then the remaining days, measured with real month lengths so the month count is exact. The total-days figure is the plain day count since birth.