Age Calculator
Exact age in years, months, days
The Age Calculator returns the exact age between a birth date and a target date (defaulting to today). It expresses the result in multiple useful forms: years + months + days, total days, total weeks, and total hours.
Useful for filling out forms, calculating eligibility, planning birthdays, and a few less common uses like figuring out exactly how many days you have been alive (a slightly humbling number).
What it returns
- Age in completed years, months, and days.
- Total days lived.
- Total weeks.
- Total hours.
- Next birthday and days remaining.
How it works
The calculator counts the elapsed time accounting for month lengths and leap years. The years/months/days breakdown subtracts birth year/month/day from the target, then borrows from months and years to keep day and month differences non-negative — the same algorithm used by spreadsheets' DATEDIF function in "YMD" mode.
Worked example
If today is November 27, 2026 and you were born on March 14, 1990:
- 36 years, 8 months, 13 days
- ≈ 13,407 days
- ≈ 1,915 weeks
- ≈ 321,768 hours
- Next birthday: 107 days away
When this is useful
Confirming your exact age on a particular date (visa applications, school enrollment cutoffs, insurance), curiosity about time elapsed, and calculating age differences between two people or events.
Time zones and leap years
The calculator uses calendar arithmetic on the dates you enter and ignores time zones. Leap years (every 4 years, minus century years not divisible by 400) are handled correctly. The "total days" value is exact down to whole days.
Frequently asked questions
Why does the month count "borrow" days?
When the target day is less than the birth day, the calculator subtracts a month and adds the days in that month. This keeps the breakdown intuitive — never showing negative days.
How is "next birthday" calculated for Feb 29 births?
In non-leap years, Feb 29 is treated as Mar 1 for "next birthday" purposes. Different jurisdictions handle this differently for legal age.
Can I calculate age at a future date?
Yes. Change the "as of" date to any future date.