Your age is the number of full birthdays you have had: subtract the birth year from the current year, then subtract one more if this year's birthday hasn't arrived yet. This calculator does that and goes further, giving the exact age in years, months and days, the total days and weeks lived, the weekday you were born and the date of your next birthday.
For example, someone born on July 15, 1990 is 36 years, 3 months and 26 days old on November 10, 2026, or 13,267 days. Leap years are handled by the Gregorian calendar rules.
How to use the age calculator
- Enter the date of birth.
- Leave "Age on this date" as today, or change it to see an age on any other date (for example, a deadline or an event).
- Read the age, the exact years-months-days breakdown, the totals and the next birthday.
Formula
When a month is shorter than the birth day (for example a 31st birthday-day in a 30-day month, or February 29 in a common year), the month is counted at that month's last day. This is one convention; some legal systems treat a February 29 birthday as March 1 in common years.
Worked example
Born July 15, 1990; age on November 10, 2026.
- Whole months: (2026 − 1990) × 12 + (11 − 7) = 436, but the 15th hasn't been reached on the 10th, so 435 months.
- 435 months = 36 years 3 months, ending October 15, 2026.
- October 15 to November 10 = 26 days.
- Total: 13,267 days (1,895 weeks 2 days). Next birthday: July 15, 2027, in 247 days.
Leap years and age
Under the Gregorian calendar rule described by the U.S. Naval Observatory, years divisible by 4 are leap years, except century years not divisible by 400. So 2000 was a leap year but 1900 and 2100 are not. The day counts here include every leap day between the two dates.
To count days between any two dates (not just from a birthday), or to add days to a date, use the date difference calculator (days between dates). For hours and minutes worked in a shift, use the time duration calculator (hours between two times).
Age milestones
Some people celebrate round numbers of days: 10,000 days old is about 27 years and 4 months, and 20,000 days is about 54 years and 9 months. Enter a birth date and use the date difference calculator (days between dates) in add mode (add 10,000 days) to find the exact date.
Caveats and assumptions
- Uses calendar dates only, not birth time or time zones.
- February 29 birthdays are counted on February 28 in common years; legal age rules can differ by jurisdiction.
Frequently asked questions
How do I calculate my age?
Subtract your birth year from the current year, and subtract 1 more if you haven't had this year's birthday yet.
How many days old am I?
Enter your birth date; the "Also equal to" line shows the total days, counting leap days.
How is age calculated for someone born on February 29?
This calculator counts the birthday on February 28 in non-leap years. Some laws use March 1 instead.
Can I calculate age on a future date?
Yes. Change "Age on this date" to any date to see how old someone will be (or was) then.
What day of the week was I born?
Enter your birth date; the calculator shows the weekday.
Sources
- U.S. Naval Observatory — Leap Years — Gregorian leap year rule
This calculator gives estimates for planning and education. Check measurements, local codes, supplier specs and your school's official policy before relying on a result. See our disclaimer and how we build and check calculators.