How to Calculate Age From Date of Birth

The method in three steps

1. Years: count the birthdays that have passed by the age date.
2. Months: count the whole months since the last birthday.
3. Days: count the days since that date in the month.

If the day of the month has not been reached yet, borrow one month and add the number of days in the month just before the age date. If the month has not been reached, borrow one year and add 12 months. This is how people and offices usually count age by hand, and it is the method the calculator uses.

Worked example

Born on 15 March 2000. Age on 2 November 2026:

Years:  2026 - 2000 = 26 (the birthday on 15 March 2026 has passed)
Months: November (11) - March (3) = 8, but 2 November is before the 15th, so 7 whole months
Days:   borrow October (31 days): 2 + 31 - 15 = 18

Age: 26 years, 7 months and 18 days

The calculator also shows the totals. For the same dates:

Total days are counted exactly, with every leap year included. Total months is simply the years x 12 plus the leftover months.

Age on any other date

The calculator counts your age on today by default, using your device's date. Change the second date to find your age on any day in the past or future, for example the last date of a form or a school's admission cut-off. If your phone's date is wrong, set the second date by hand.

For government job notices, with a lower and upper age limit and category relaxation, use the Government Exam Age Calculator instead. It counts age the same way, and also checks the limit and shows the born-between dates.

Born on 29 February

In years without 29 February, the calculator counts the birthday on 1 March. Someone born on 29 February 2004:

Some offices count a 29 February birthday on 28 February instead. If a form or an office uses that rule, follow it. The total age in days is exact either way.

Why another site may be one day different

Months have 28, 29, 30 or 31 days, so the leftover days near the end of a month can be counted in more than one way. Some sites count forward from the birth date, others count back from the age date. The calculator counts back from the month just before the age date. The years are the same everywhere; only the leftover days can differ.

Child's age in months

For school admission or vaccination, the age in months is often what matters. Read the In months figure, or look at the years and months together. A child born on 20 August 2024 is 2 years and 2 months old on 3 November 2026, which is 26 months. On that day the calculator shows 2 years, 2 months and 14 days, because 14 days have passed since the 20th of the month before.

Day of the week you were born

The calculator shows the weekday of your date of birth under your age. 15 March 2000 was a Wednesday, and 29 February 2004 was a Sunday.

Common questions

How do I calculate my age from my date of birth? Count completed years, then the months since your last birthday, then the days since that date in the month.

Can it go back before 1900? No. It accepts dates from the year 1900.

Is my date of birth saved? No. The calculation happens in your browser, and nothing is stored or sent.