How to Calculate Your Exact Age
Calculating age sounds simple — subtract your birth year from the current year. But that only gives a rough number. Your exact age depends on the month and day as well. This calculator does the full date arithmetic for a precise result down to the day.
The Date Difference Method
Break the problem into three parts:
- Years: Subtract birth year from current year, reduce by one if you haven't yet reached your birthday this year.
- Months: Subtract birth month from current month. If negative, borrow 12 from the year count.
- Days: Subtract birth day from current day. If negative, borrow the number of days in the previous month.
Age in Different Units
Beyond years-months-days, you might want to know total days alive, total weeks, or even hours and minutes. The calculator shows all of these. Parents often track a baby's age in weeks for the first year, and "10,000 days alive" has become a popular personal milestone.
Handling Leap Years
A leap year occurs every 4 years (with century exceptions), adding February 29. If born on Feb 29, your birthday in non-leap years typically falls on Feb 28. The total-days calculation includes all leap years automatically.
Common Uses
- Legal age verification: Determine if someone has reached 18, 21, or 65 on a given date
- Retirement planning: Calculate exact age at a future retirement date
- Insurance forms: Many require age in years and months
- Milestone tracking: Find when you'll hit 10,000 days or 1,000 weeks alive
Age Formula
For total days: totalDays = floor((endDate - birthDate) / 86400000)
For years/months/days, the calculator uses calendar-aware subtraction with borrowing, similar to how you'd subtract multi-digit numbers but across months of varying lengths.