Age Calculator
Calculate exact age in years, months, and days between a birth date and any reference date, with total weeks, days, hours, minutes, and seconds.
Age Calculator
Enter a date of birth and an “age as of” date to find exact age and elapsed time.
How age is counted
Age in years, months, and days uses calendar arithmetic: subtract birth date from the reference date, borrowing days from the previous month when needed.
How to use this age calculator
- Date of birth: Enter the month, day, and year you were born (or the start date for any elapsed-time calculation).
- Age as of: Enter the reference date. Click Today to use the current date instantly.
- Calculate: See age in years, months, and days, plus total weeks, days, hours, minutes, and seconds in the step-by-step breakdown.
How age is counted
Most official age calculations use calendar age: the difference between two dates expressed in whole years, months, and days. This is not the same as dividing total elapsed time by fixed-length years.
The years–months–days breakdown works like manual date subtraction:
- Subtract the birth day from the reference day. If the result is negative, borrow the number of days in the previous month and reduce the month count by one.
- Subtract birth month from reference month. If negative, borrow 12 months and reduce the year count by one.
- Subtract birth year from reference year to get the remaining whole years.
Example: Born January 1, 2000, age as of July 2, 2026 → 26 years, 6 months, 1 day. The same span is also 9,679 days (about 1,382 weeks), or roughly 232,296 hours and 836,265,600 seconds at midnight on both dates.
Leap years are handled automatically: February 29 birthdays are valid, and February in leap years has 29 days when borrowing.
Calendar age vs. elapsed time
- Years, months, days: Human-readable calendar units. A “month” follows the actual calendar (28–31 days), not a fixed 30-day block.
- Total days / weeks: Whole calendar days between the two dates (midnight to midnight).
- Hours, minutes, seconds: Derived from the exact millisecond difference at midnight on each date.
For legal or medical purposes, always confirm which definition applies in your jurisdiction — some systems use only whole years, or age at the next birthday.
Real-world uses
- Birthdays: Find exact age on a specific date or plan milestone celebrations.
- Forms and eligibility: Verify minimum age for school enrollment, driving, voting, or retirement.
- Genealogy and records: Compute age at historical events or between family milestones.
- Project timelines: Measure how long something has existed since a launch or founding date.