How baby age is counted
Doctors and health visitors usually describe a baby’s age in weeks for the first couple of months, then in months until about 2 years. A baby is 1 month old on the same date in the following month. For example, a baby born on 10 March is 1 month old on 10 April.
Why age in months matters
Milestones, growth charts, feeding advice and check-ups are all based on age in months. Our month by month guide shows what to expect at each stage.
Born early?
For babies born before 37 weeks, doctors often use corrected age for growth and development. Use our Corrected Age Calculator.
Frequently asked questions
How old is my baby in weeks?
The calculator shows your baby’s age in full weeks and days, which is how age is often given in the first months.
When is my baby 1 month old?
On the same date in the next calendar month. If that date does not exist, such as 31 February, it is the last day of that month.
Is my information saved?
No. The calculation runs in your browser and nothing is stored.
References
CDC: Developmental milestones