Age Calculator
Calculate age from a birth date to an as-of date with calendar, birthday, and exact elapsed-time breakdowns.
Enter a birth date and the date to calculate age as of. The calculator stays on this page and is useful for birthdays, eligibility checks, membership windows, school or sports age bands, and quick planning summaries.
Use the person's calendar birth date.
Use today, a future eligibility date, or a past record date.
Optional. Leave blank to calculate from the start of the birth date.
Optional. Leave blank to calculate at the start of the as-of date.
Choose how February 29 birthdays are treated when the target year is not a leap year.
Adds milliseconds, minutes, hours, and days to the generated summary.
How it works
The calculator compares the birth date/time with the as-of date/time and reports completed calendar years, then completed months, then the remaining days and time. This matches how people usually describe age while still showing exact elapsed totals when requested.
Optional time fields let you calculate age before or after the birth time on a birthday. If you leave the time blank, the calculation uses the start of that local calendar date.
Leap-day birthday rules vary by jurisdiction, organization, and policy. Choose the February 29 handling that matches the rule you need, and verify legal, medical, school, travel, or eligibility decisions against the authoritative policy for your situation.
