Enter your date of birth (and optionally a different "as of" date) to get your exact age in years, months and days, the total days you've lived, and how long until your next birthday.
Pick your date of birth and press Calculate age.
How exact age is calculated
Chronological age is the difference between two calendar dates, expressed in whole years, then the leftover months, then the leftover days. The method works backwards from the largest unit:
years = asOf.year − birth.year
months = asOf.month − birth.month
days = asOf.day − birth.day
If days comes out negative, borrow a month (adding the number of days in the previous month) and reduce months by one. If months is then negative, borrow a year and add 12 months. The result is the precise age people mean when they say "35 years, 11 months and 24 days".
Worked example
Born 15 June 1990, measured on 9 June 2026:
Years: 2026 − 1990 = 36, but the June 15 birthday hasn't happened yet in 2026.
Day is negative (9 − 15), so borrow a month: age becomes 35 years, 11 months, 25 days.
Total days lived: about 13,143 days.
Months and leap years
Because months have different lengths (28–31 days) and leap years add a February 29th, "one month" isn't a fixed number of days. This calculator borrows the correct number of days from the actual previous month, so the year/month/day breakdown always lands on real calendar dates. The "total days lived" figure counts every calendar day, including leap days.
Tip: leave the second field blank to use today's date, or set it to a future or past date to find someone's age at any moment — handy for eligibility cut-offs and anniversaries.
Frequently asked questions
How do you calculate exact age?
Subtract the birth date from the target date year by year, then month by month, then day by day, borrowing from the next-larger unit whenever a difference comes out negative. The result is age in whole years, months and days.
How are leap years handled?
The calculator works with real calendar dates, so February 29ths and varying month lengths are counted correctly. Total days lived includes every leap day between the two dates.
Can I find my age on a past or future date?
Yes. Set the "age as of" field to any date — past or future — to find how old someone is or will be on that day. Leave it blank to use today.
How many days are in a year on average?
A calendar year averages about 365.25 days once leap years are included, which is why total-days figures don't divide evenly into whole years.
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Mustafa Bilgic · Editor, Calcool Age is computed from the proleptic Gregorian calendar used worldwide for civil dates. All math runs in your browser using your device clock; nothing is sent anywhere. Edge cases (Feb 29 birthdays) follow the common convention of rolling to Mar 1 in non-leap years.