Enter your baby’s date of birth to see their age in months, weeks and days. It works for newborns, infants, toddlers and older children, and includes an optional corrected age for babies born early.
Enter your baby’s date of birth and select “Calculate baby’s age” to see the result.
Doctors, nurses and parents usually describe a young baby’s age in weeks, a growing baby’s age in months, and switch to years around the second birthday. This baby age calculator shows months, weeks and days together, so you can answer a form, follow a checkup or vaccination schedule given by your doctor, fill in a daycare application or keep a milestone diary without counting on a calendar.
The calculator counts completed calendar months from the date of birth, then the remaining days. Weeks come from the total number of days divided by seven, rounded down, with the leftover days shown separately.
Age = completed months + remaining days
Weeks = total days ÷ 7Months have different lengths, so a month-based age and a week-based age can look slightly different. About 4 months is roughly 17 weeks, not exactly 16 or 18.
Date of birth: 5 January 2026
Calculate on: 20 May 2026
5 Jan → 5 May = 4 completed months
5 May → 20 May = 15 days
Total = 135 days = 19 weeks and 2 days
Baby’s age = 4 months and 15 days (19 weeks, 2 days).
A baby born early may be given a corrected (or adjusted) age, which counts from the due date instead of the birth date. Add the due date in the optional field to see the actual age and the corrected age together. For example, a baby born on 15 February 2026 with a due date of 1 April 2026 is 5 months and 17 days old by birth date on 1 August 2026, and 4 months and 0 days old by corrected age. How corrected age is used is decided by your doctor or health visitor, so treat this as a calendar calculation, not medical advice.
These values use an average month of about 30.4 days.
| Age in months | Weeks | Days |
|---|---|---|
| 1 month | about 4 | about 30 |
| 2 months | about 9 | about 61 |
| 3 months | about 13 | about 91 |
| 4 months | about 17 | about 122 |
| 6 months | about 26 | about 183 |
| 9 months | about 39 | about 274 |
| 12 months | about 52 | about 365 |
| 18 months | about 78 | about 548 |
| 24 months | about 104 | about 730 |
Enter the date of birth. The calculator counts completed calendar months from the birth date and shows the remaining days, for example 4 months and 15 days.
The result shows full weeks plus the extra days. Weeks are the total number of days lived divided by seven, rounded down.
Corrected age counts from the due date instead of the birth date. Add the due date in the optional field to see the actual age and the corrected age side by side. Ask your doctor or health visitor how corrected age applies to your baby.
Yes. After the second birthday the result switches to years, months and days, so it works as an age calculator for a child. Use “Calculate age on” to check a child’s age on a school or activity cutoff date.
The result includes total days lived. To compare two people’s ages in days, use the age in days calculator.
No. It is a calendar calculator. It does not assess growth, development or health, so ask your doctor or health visitor about any medical question.
No. The calculation runs in your browser and the dates are not uploaded or saved by this website.