Age Calculator
Enter a date of birth and the date on which you want to know the age. The result changes completed years on the birthday and shows the next-birthday countdown.
General calendar result only. Legal age can depend on local law and the exact purpose. For February 29 births, this tool advances age on March 1 in non-leap years and states that assumption in the result.
Enter your scenario
Use the details that match your situation. Your estimate stays in this browser.
How this estimate works
- The calculator starts with the difference between the two calendar years.
- It subtracts one when the birthday for the selected year has not yet occurred, so completed age changes on the birthday.
- Gregorian calendar ordinals provide total elapsed days and the next-birthday countdown without timezone effects.
Official references
- UK Government Analysis Function: age and date-of-birth harmonised standard
- U.S. Naval Observatory: Gregorian calendar and leap-year rule
Government statistical guidance recognizes completed age as something derived from date of birth for a specified date. Confirm jurisdiction-specific legal treatment separately.
Frequently asked questions
Does age change before or on the birthday?
This calculator increases completed age on the birthday. The day before, it reports one fewer completed year.
How are February 29 birthdays handled?
In a non-leap year this general calculator treats March 1 as the birthday. Legal rules can use a different convention, so confirm them for official purposes.