Age in months
The calculator counts the whole months from the date of birth to the chosen date, and the days that are left over. A baby born on 10 January 2026 is 3 months and 5 days old on 15 April 2026. The age in months is the number you see on forms, trackers and registration pages for babies and toddlers.
How the months are counted
A month is complete on the same day of the next month. A baby born on the 10th has a monthly birthday on the 10th of each month. When the month is too short for the day, for example a birth on the 31st, the last day of the month is used.
Months, weeks and days
The result also shows the age in weeks and days, which is how very young babies are often described, and the age in months as a decimal number.
Months and years
| Months | Years |
|---|---|
| 6 | 0.5 |
| 12 | 1 |
| 18 | 1.5 |
| 24 | 2 |
| 36 | 3 |
| 60 | 5 |
Next monthly birthday
The tool shows the date on which the next month is completed and the days to go, so you can plan a monthly photo or a check-up date.
Premature babies
This calculator uses the date of birth only. It does not adjust for a premature birth. Ask your doctor or nurse which age to use for a baby who was born early.
Related calculators
For years, months and days together, use the age calculator. See age in days, age in years and weeks between dates.