Age Calculator
Written by Thierno Sadou Diallo, formula verified per our methodology • Last checked on 9/3/2026
Your age in full years is calculated by counting the complete years elapsed from your date of birth to today — the current year only counts if your birthday has already passed.
Explanation
Calculating age seems trivial (current year minus birth year), but this shortcut is wrong for several months every year: as long as the birthday hasn't happened yet in the current year, you need to subtract one year from the result. This calculator compares the month and day of the birth date to those of today's date to determine whether the birthday has already occurred. One special case handled explicitly: someone born on February 29 only has a "real" birthday one year in four — in non-leap years, their age only increments on March 1, not February 28. The number of days lived is a simple calendar count between the two dates. For other everyday calculations, see also our tip calculator and our rule of three calculator.
Example: born on June 15, 1990
Inputs
Date of birth: June 15, 1990.
Calculation
If today's date is on or after June 15 of the current year, the birthday has already passed: the current year is counted. Otherwise, one year is subtracted from the raw result (current year − 1990).
Result
Someone born on June 15, 1990 is, for example, 35 from January 1 to June 14 of a given year, then turns 36 starting June 15 of that same year.
Frequently asked questions
Why doesn't my age simply equal "current year minus birth year"?
Because that subtraction doesn't account for the birthday. Someone born in December 1990 only reaches their "expected" age in December: from January to November, they're still one year younger than that simple calculation suggests.
How is the age of someone born on February 29 calculated?
February 29 only exists in leap years (roughly one year in four). In other years, this calculator treats the birthday as not yet reached on February 28, only acquiring it on March 1 — this is the most common convention, notably used under French law for the age of legal majority.
Does the number of "days lived" include the day of birth?
The calculation counts the calendar days elapsed between the date of birth and the reference date (today). The day of birth itself counts as 0 days lived, and each following calendar day adds one.
Can this calculator find an age on a specific past or future date?
No: this calculator always uses today's date as the reference. For an age on an arbitrary date (for example, the exact age at the time of a past event), the calculation stays the same but uses that date as the reference instead of today.