Calculator
Age Calculator
Find your exact age in years, months and days, and how long until your next birthday.
How is exact age calculated?
Age in years/months/days isn’t just today’s date minus your birth date — months have different lengths and years have leap days, so a simple subtraction gives the wrong answer more often than not. This calculator works date-by-date to get the actual elapsed years, months and days right.
Frequently asked questions
Why doesn't a simple subtraction work for age?
Subtracting birth year from the current year ignores whether the birthday has happened yet this year, and subtracting dates naively breaks when months have different numbers of days (going from January 31 to March 1 isn't "1 month" in a simple subtraction). Proper age calculation borrows from the next larger unit, the same way you'd borrow in manual subtraction.
How is total days lived calculated?
It's the straight difference between the two dates in milliseconds, converted to days — a simple count that doesn't need the years/months/days breakdown logic, since total elapsed time is unambiguous regardless of calendar quirks.
How does the next-birthday countdown work?
The calculator takes your birth month and day, applies it to the current year, and checks if that date has already passed. If it has, it uses next year's date instead — then counts the days from today to whichever date is correct.
What happens if someone is born on February 29?
Leap-year birthdays are a genuine edge case. In non-leap years, most calculations treat the "next birthday" as either February 28 or March 1 depending on convention — this calculator uses the JavaScript date engine's default behavior, which rolls February 29 forward to March 1 in non-leap years.