Baby Age in Weeks Calculator
Calculate your baby's exact age in weeks, days, and months from their date of birth to today or any date.
How It Works
Enter your baby's date of birth. The calculator computes the exact age in weeks and days, which is especially useful in the first year when pediatricians and growth charts use weeks rather than months.
Formula
Age in Weeks = (Target Date − Birth Date) ÷ 7
Frequently Asked Questions
Why do doctors measure baby age in weeks?
In the first 2 years, weekly measurements are more precise for tracking growth and development. Growth charts for infants use weeks, and feeding recommendations often reference specific week ranges.
How many weeks old is a 3-month-old baby?
A 3-month-old is approximately 13 weeks old. The conversion is not exact because months have different numbers of days. Use this calculator for the precise week count.