📅 Baby Age Calculator: Weeks, Months & Days

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Fill in the details and click Calculate to see your results.

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📘 About the Baby Age

Babies' ages are counted in weeks for the first three months, then in months until age 2. Enter the date of birth to get the exact age in years, months and days, in weeks and in total days.

The calculator also lists the dates of upcoming milestones such as 100 days, the half-birthday and the first birthday.

✏️ Worked example

Born 15 July 2025, age on 15 January 2026

You enter
Date of Birth15 Jul 2025
Age on Date15 Jan 2026
You get
Baby's age6 months 0 days
In weeks26 weeks 2 days
In days184 days
In months6 completed months
Born on aTuesday

6 months 0 days; 26 weeks 2 days.

Try this example →

❓ Frequently asked questions

How many weeks old is a 3-month-old baby?

About 13 weeks.

When is my baby 100 days old?

Add 100 days to the birth date — the calculator shows the exact date.

Is a 6-month-old 24 or 26 weeks?

About 26 weeks: months are longer than 4 weeks (a month averages 4.35 weeks).