Age Calculator
Enter a date of birth and this calculator returns the exact age in years, months, and days as of today (or any date you choose). It also shows the total number of days lived and how long until the next birthday.
Exact age matters more often than you might think. Eligibility cutoffs for school enrollment, sports categories, visas, retirement benefits, and medical dosing all hinge on age down to the day. Calculating it by hand is error-prone because months have different lengths and leap years shift the count.
How it's calculated
Age = target date − birth date, in calendar years, months, and days
The calculation counts full calendar years first, then full months, then remaining days, the same way ages are stated legally. Leap years are handled automatically by counting real calendar dates rather than assuming 365-day years.
Worked example
Someone born on 15 March 1990 is, on 30 August 2026, exactly 36 years, 5 months, and 15 days old, a total of 13,317 days. Their next birthday is 197 days away.
Frequently asked questions
›How are leap-year birthdays handled?
People born on 29 February simply have their age tick over on 1 March in non-leap years for legal purposes in most countries. The day count here always uses real calendar dates, so nothing is lost or double-counted.
›Why do different sites give slightly different month/day breakdowns?
There is more than one convention for borrowing days across months of different lengths. The differences are at most a day or two; the total-days figure is unambiguous.
›Can I calculate age at a past or future date?
Yes. Change the "age at date" field. This is useful for forms that ask your age on a specific cutoff date, such as a competition or enrollment deadline.
›How many days old is a person on their 18th birthday?
6,574 days if the span includes 4 leap days, or 6,575 with 5. Whether it is 4 or 5 depends on where the birth year falls in the leap-year cycle.
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