Baby age calculator
Exactly how old is your baby — in days, weeks, and months? Add the original due date for babies born early and get their corrected age too.
Pick your baby’s birth date to see their age.
How baby ages are counted
By convention, baby ages run in weeks for about the first three months, then months until the second birthday, then years. “14 weeks” and “3 months” can describe the same baby — weeks count in exact sevens while months follow the calendar, which is why the two drift apart.
What is corrected age?
Babies born before 37 weeks get two ages: actual (from the birth date) and corrected (from the due date). Development follows the corrected clock — so when you read a milestones guide, corrected age is the honest place to look until around age 2. Checkup schedules, on the other hand, go by actual age.
Frequently asked questions
How do I calculate my baby’s age in months?
Count full calendar months from the birth date, then the days left over. A baby born on 15 January is exactly 6 months old on 15 July — if the birth date doesn’t exist in a month (born the 31st), the month ticks over on that month’s last day.
Why do people give babies’ ages in weeks?
Early development moves fast, so weeks are the common currency for roughly the first three months. After that, months take over, and from age two most people just use years.
What is corrected age?
For babies born early, corrected age counts from the original due date instead of the birth date. A baby born 8 weeks early who is 12 weeks old has a corrected age of 4 weeks.
Which age should I use for milestones?
Corrected age. A baby born two months early sits, crawls, and babbles on their due-date clock, not their birthday clock. Routine checkups, though, are scheduled by actual age.
When does corrected age stop mattering?
Most children born early catch up to their peers by around age 2, and from then on everyone uses actual age. Your paediatrician may advise differently for very early arrivals.
See what’s typical for each month in the baby milestones guide, check where their measurements sit with the growth percentile calculator, plan daytime sleep with the nap schedule calculator, or check sleep needs by age. Every child develops at their own pace — if your baby loses skills they had, talk to your paediatrician promptly.