About the Baby Age Calculator
Your baby’s exact age in weeks, months and days, plus adjusted age for premature babies.
Also known as: how old is my baby, baby age in weeks, age in months calculator, child age calculator, age-in-weeks, age-in-months.
How to use this calculator
- Enter date of birth, today, weeks born early (if premature).
- The result updates instantly as you type — press Calculate (or Enter) at any time.
- Review the breakdown shown under the main result.
- Use Copy result or Share to save the answer or send a link with your inputs.
Formula
Age = today − date of birth (corrected age subtracts weeks born early)
Worked example
Using the values pre-filled in the calculator above:
- Date of birth: 2026-05-25
- Today: 2026-09-22
- Weeks born early (if premature) = 0
the calculator returns:
- Age: 3 months 28 days
- In weeks: 17.1
- In days: 120
- In months: 3.9