How the Baby Age Calculator Works
Enter your baby's date of birth and the calculator works out their exact age in weeks, months and days. In the first two years, milestones, feeding stages and check-ups are usually described in weeks and months rather than years, so a plain 'age in years' isn't much help.
Baby Age Can Be Shown In
Days, weeks, months, hours, or a combined 'months and days' figure. The calculator shows all of them at once, so you can use whichever your doctor, nursery or app asks for.
Corrected Age for Premature Babies
If a baby was born early, doctors often talk about 'corrected age': the age counted from the original due date rather than the birth date. Add the due date in the optional field above and the calculator shows both figures. Your paediatrician will tell you when to use which.
Example
A baby born on 1 January 2026 is 3 months old on 1 April 2026. That's 90 days, or 12 weeks and 6 days.
Frequently Asked Questions
Q: How many weeks old is my baby?
A: Enter your baby's date of birth into the calculator above. It shows the exact number of weeks and extra days since birth.
Q: How do I calculate my baby's age in months?
A: Count whole calendar months from the birth date. A baby born on 1 January is 3 months old on 1 April. Dividing days by 30 gives a slightly wrong answer because months vary between 28 and 31 days.
Q: What is corrected age?
A: For babies born early, corrected age is the age counted from the original due date instead of the birth date. It's commonly used for the first two years or so; ask your paediatrician how it applies to your baby.
Q: Why do parents track age in weeks?
A: Babies change quickly in the first months, so weeks give a finer picture than months. Many growth and feeding guides are organised by weeks up to about three months.
Q: Is this calculator medical advice?
A: No. It only calculates age from dates. Milestone hints are general encouragement, and every baby develops at their own pace. Speak to your doctor or health visitor with any concerns.