Tools · Baby
Baby Age Calculator: How Many Weeks or Months Old Is My Baby?
Free baby age calculator. Enter your baby's date of birth to see their exact age in months, weeks, and total days — plus corrected (adjusted) age for babies born prematurely.
Add this only if your baby was born early, to see corrected age.
Enter your baby's date of birth to see their age.
How your baby's age is calculated
This calculator shows your baby's chronological age — the time since birth — in three ways: completed months plus leftover days, total whole weeks, and total days. Weeks are the unit most often used in the first few months ("my baby is 10 weeks old"), while months become more common later.
If your baby was born early, enter the original due date to also see the corrected (adjusted) age. Corrected age subtracts the weeks of prematurity from chronological age, giving a fairer picture of where your baby is developmentally. For example, a baby born 8 weeks early who is 4 months old chronologically has a corrected age of about 2 months.
Health professionals often use corrected age when discussing growth and developmental milestones for premature babies, typically until around 2 years of age. Chronological age is still used for scheduling vaccinations. Everything is calculated on your device — nothing is stored or uploaded.
Frequently Asked Questions
How is my baby's age calculated?
Chronological age is counted from your baby's date of birth to today. This tool shows it as completed months plus remaining days, as total weeks, and as total days. Months are counted by the calendar (so the day-of-month is preserved), which is why a baby born on the 15th 'turns' a new month on the 15th.
What is corrected (adjusted) age?
Corrected age applies to babies born prematurely. It's your baby's chronological age minus the number of weeks they were born early. If you enter the original due date, this calculator computes it for you. Corrected age gives a more realistic expectation for developmental milestones, because a baby born two months early has had two fewer months to develop than a baby born on time.
When do I stop using corrected age?
Most clinicians use corrected age when assessing growth and development until about 2 years of age, by which point most healthy children born prematurely have caught up. Your pediatrician may adjust this timeframe based on how early your baby was born. Always follow your provider's guidance.
How many weeks old is my baby in months?
As a rough guide, 4 weeks is about 1 month, 8 weeks about 2 months, and so on — but weeks and calendar months don't line up exactly (a month averages about 4.3 weeks). This calculator shows both at once so you don't have to convert. For medical purposes, weeks are usually preferred in the early months.
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