Age Calculator

1. 1Enter the date of birth.
2. 2Leave the second date as today, or set it to work out an age on a particular date.
3. 3Read the exact age, followed by the totals and the next birthday countdown.

Age is counted the way people actually count it: whole years first, then whole months, then the days left over. The tool takes the year difference, subtracts one if the birthday has not happened yet this year, then borrows days from the previous calendar month when the day-of-month has not been reached.

Borrowing from the real previous month is what makes the result correct across months of different lengths. A person born on 31 January is 1 month old on 28 February in a common year, because February has no 31st.

Leap years are handled by the calendar itself rather than by assuming 365.25 days. Someone born on 29 February has their anniversary treated as 1 March in common years, which is the most widely used convention.

Someone born on 15 March 2001, checked on 5 September 2026

1. Enter 15 March 2001 as the date of birth.
2. Leave the second date as 5 September 2026.

Result: 25 years, 5 months and 21 days — 9,305 days in total, with the next birthday 191 days away.