Baby age calculator
Your baby's exact age in weeks, months and days, plus the date they turn another month and the next well-baby check-up (AAP schedule).
Born early? Use the adjusted age calculator too.
Enter a birth date.
Weeks, months and the "fourth trimester"
The first 12 weeks after birth are sometimes called the fourth trimester: babies are still adjusting to life outside the womb and development is counted in weeks. Growth spurts are commonly reported around 2–3 weeks, 6 weeks and 3 months, when babies may feed more often for a few days.
See what to expect at this age with baby milestones by month and wake windows by age.
Frequently asked questions
How do you count a baby's age in weeks?
Count the days since birth and divide by 7. A baby born 45 days ago is 6 weeks and 3 days old. In the first few months, health professionals usually talk in weeks; after about 3 months they switch to months.
When is my baby one month old?
On the same date in the following month: a baby born on 10 March is one month old on 10 April. That's between 4 and 4.4 weeks depending on the month, which is why "4 weeks" and "1 month" aren't quite the same.
How do I calculate age for a premature baby?
Use corrected (adjusted) age for growth and development until about age 2: subtract the number of weeks your baby was born early from their actual age. Our adjusted age calculator does this for you.