How old is your baby?
Enter their birthday. You’ll see their age in months, weeks and days, and when they turn the next month.
Born before 37 weeks? Pick the week, and you’ll see their corrected age too.
Enter the birthday, and their age shows up here.
- In weeks
- In days
- Corrected age
Your dates stay on this device. Nothing is sent anywhere.
Baby age, in plain words.
Count the days since they were born and divide by seven: 100 days is 14 weeks and 2 days. Or enter the birthday above and the calculator does it for you.
By the calendar. A baby born on 10 March is one month old on 10 April and two months old on 10 May. Born on the 31st, they turn a month on the last day of a shorter month, like 30 April.
For a baby born early, it’s their age counted from the due date instead of the birthday. The American Academy of Pediatrics’ way to work it out: take your baby’s age in weeks and subtract the number of weeks they were born early (40 minus the weeks of pregnancy at birth). A baby born before 37 weeks counts as premature (WHO), which is where the calculator starts showing it.
Sources: AAP, corrected age for preemies and WHO, preterm birth.
Through the first 2 years, the AAP says, for things like growth and milestones. For babies born very small, under 1,000 g, doctors often keep using it until age 3. Your paediatrician will tell you when to stop.
Sources: AAP, corrected age for preemies and the US Maternal and Child Health Bureau’s growth chart training.
When you enter a birthday here, this device remembers the age in months, and the sleep calculator starts there. For a baby born early, it uses the corrected age.
Planning naps?Sleep calculator
Their age is exact. Their days aren’t.
Baby’s Day In logs every feed, nap and nappy with one tap, then shows the pattern week by week. So you see what this age looks like for your baby.
See the weekly viewEvery day of it, in one place.
Free while we’re in early access. Two phones, no extra hardware.