Working out an age sounds trivial — subtract the birth year from this year — until you need it to be *exact*, in years, months and days, and the birthday hasn't happened yet this year. Then the little edge cases start to bite.
Here's how to calculate age correctly, the gotchas to watch for, and the easy way to get an exact answer.
The quick method (and its flaw)
The rough version is: current year − birth year. But that's only right if the birthday has already passed this year. If it hasn't, you've counted a year too many. The fix: subtract one if today is *before* this year's birthday. That gives the correct age in whole years.
Exact age in years, months and days
For a precise age, work down the units: subtract the years, then the months, then the days — and 'borrow' when a value goes negative (much like long subtraction). If the day-of-month comes out negative, borrow a month; if the month comes out negative, borrow a year. Doing this by hand is fiddly, which is exactly why a calculator helps.
The leap-year gotcha: people born on February 29 technically only have a 'real' birthday every four years. Most systems treat their birthday as Feb 28 (or Mar 1) in common years — worth knowing when a date looks off by a day.
Calculate it instantly
Enter a birth date and get an exact age in years, months and days with the free Age Calculator — it handles the borrowing and leap years for you.
Age CalculatorFind your exact age in years, months and days.Related date calculations
- Date Difference Calculator — the exact gap between any two dates.
- Add or Subtract Days — find the date a number of days before or after another.
- Countdown Timer — count down to a birthday, deadline or event.
- Time Duration Calculator — the length between two times.