Age Calculator

How it works

Enter a date of birth. The as-of date defaults to today and can be changed to any other date.

When this question comes up

Age in years is enough for most forms, but not for everything. Paediatric dosing, visa and passport rules, sports age groups and pension eligibility all turn on the exact year, month and day. Some of those rules cut off on the birthday itself and others on the day before, so a single day can decide the answer.

Rules and limits

• Age is counted the civil way: whole years first, then whole months, then the remaining days.
• The as-of date defaults to today in your device's time zone.
• A date of birth later than the as-of date is rejected instead of showing a negative age.
• For a 29 February birthday, the age rolls over on 1 March in non-leap years.

Worked example

Born 29 Feb 2000, as of 1 Mar 2026 = 26 years, 0 months, 0 days

Checking the result by hand

Subtract the birth year from the reference year, then check whether this year's birthday has already passed. If it has not, take off one year and add twelve months. Then subtract the birth month and day to get the remainder. Someone born on 29 February is usually treated as reaching a new age on 1 March in non-leap years, because there is no 29 February to reach.

FAQ