Age CalculatorYTScript

Baby Age Calculator

Enter a baby’s date of birth to see age in weeks and days, in calendar months and days, and in total days. You can also pick a date other than today.

Runs in your browser — dates never leave this device
Date of birth
Age at the date of
Age will show up here Enter a date of birth. You can change the “age at” date if you want a day other than today.

How to use it

  1. 1

    Enter the date of birth.

  2. 2

    Leave the end date as today, or pick another day.

  3. 3

    Read weeks (groups of seven days), then calendar months, then total days.

How this calculator counts age

A week on this page is seven days, so 10 days is 1 week and 3 days. A calendar month follows the same anniversary-day rule as the main age calculator; four weeks is not the same as one month.

The tool starts at birth. It does not estimate a due date, count weeks of pregnancy, or compute a corrected age for a baby born early.

Figures here are for everyday reference. They are not medical advice and should not replace guidance from a clinician.

Other date tools

Age calculatorExact age in years, months, and daysChronological age calculatorAge on an assessment date, with Y;M;D copyDog age calculatorA size-based estimate in human yearsCat age calculatorAn estimate in human years from a public chartDays between datesCount days, with or without the end dateAdd or subtract daysMove a date by years, months, weeks, or daysDay of the week calculatorWeekday, day of year, and ISO week

Questions

Why don’t weeks and months line up?

Because a calendar month is not four weeks. A baby can be 8 weeks and also 1 month and a number of leftover days, depending on the months involved.

Can I calculate age on a date in the past?

Yes. Change “age on this date” to the day you care about, such as a photo or an appointment.

Do you calculate pregnancy or corrected age?

No. This page only counts time after birth. It is not a due-date tool and it does not adjust for premature birth.