Baby age calculator.
Enter your baby's date of birth to get their exact age in weeks, months, and days. If your baby arrived early, add the original due date and you'll also get their adjusted age — the number pediatricians use when tracking milestones.
Enter a date of birth to see your baby's age.
Why weeks, and why adjusted age matters
For the first few months, a week is a meaningful unit — wake windows, feeding volumes, and growth all shift noticeably week to week. Most guidance is written in weeks up to about 12 weeks and in months after that.
For a baby born prematurely, the more useful number is adjusted age: time since the original due date. A baby born 8 weeks early who is 20 weeks old is developmentally closer to a 12-week-old, and comparing them to a 20-week-old chart will make normal development look delayed.
What changes
0–4 weeks
The newborn period. Feeding on demand, sleep spread across the whole day and night.
4–12 weeks
Wake windows lengthen, evening fussiness often peaks around 6 weeks, and the first social smiles appear.
3–6 months
Sleep starts consolidating and naps settle into a rough shape. Guidance switches from weeks to months.
6–12 months
Solids begin, naps drop from three to two, and mobility changes the whole day.
Age is the easy part. The pattern isn't.
Every chart on this site is an average for a given age. Cradle Log logs what your own baby actually does, so the numbers you plan around come from them rather than from a table.
Free on iPhone. No account, works offline.
Common questions
How many weeks old is my baby?
Count the days from your baby's date of birth to today and divide by seven. A baby born on 1 March is 4 weeks old on 29 March. The calculator on this page does it for you and also shows the age in months and total days.
Why do people count a baby's age in weeks?
In the first few months, a week makes a large difference to feeding, sleep, and development, so weeks are more precise than months. Health visitors, pediatricians, and most sleep and feeding guidance use weeks up to around 12 weeks, then switch to months.
What is adjusted age?
Adjusted age, also called corrected age, is a premature baby's age counted from their original due date rather than their date of birth. A baby born 8 weeks early who is 20 weeks old has an adjusted age of 12 weeks. Pediatricians generally track development against adjusted age for roughly the first two years.
Should I use actual age or adjusted age for milestones?
For a baby born prematurely, use adjusted age when comparing development, sleep needs, and feeding milestones, because those follow time since the due date more closely than time since birth. Use actual age for things fixed to the calendar, such as immunisation schedules, unless your pediatrician says otherwise.
When does a baby stop being a newborn?
The newborn period is usually defined as the first 28 days. After that a baby is generally described as an infant through the first year, though the terms are informal and used loosely.
Related
- Wake windows by age — chart and calculator
What the age you just worked out means for awake time.
- Growth spurt calendar
The weeks when feeding and sleep commonly go sideways.