Free online tool
Age Calculator
Calculate an exact age in years, months, and days, plus the total number of days lived.
Age is more than the current year minus a birth year. This calculator accounts for whether the birthday has occurred and for the different lengths of calendar months.
How to use it
- Enter the date of birth.
- Choose today or another date for the age calculation.
- Select Calculate age to see the calendar age and total elapsed days.
Good to know
Calendar age counts complete years and months rather than estimating every year as 365 days.
Results use the dates entered on your device and do not require an account.
Behind the answer
How this calculator works
The calculator first counts complete calendar years from the birth date to the selected date. It then counts complete calendar months after the most recent birthday and uses the actual remaining calendar days, so months with 28, 29, 30, or 31 days are handled naturally.
Total days is a separate elapsed-time calculation. That figure includes leap days that occurred between the two dates, which is why multiplying the displayed years by 365 will not usually produce the same answer.
Worked example
Someone born June 15, 2000 is 25 years, 3 months, and 15 days old on September 30, 2025. The calculation counts 25 complete birthdays, then three complete months, then the remaining 15 days.
Assumptions and limitations
- The calculation uses calendar dates, not a time of birth or time zone.
- Legal definitions of age can vary for February 29 birthdays and specific deadlines.
- A date before the birth date is not a valid age calculation.
Common questions
Why not divide total days by 365?
Calendar years are not all 365 days, and calendar months have different lengths. Official age is normally expressed in completed calendar years.
Does the calculator save a birth date?
No. The calculation runs in the browser and does not require an account.