How age is calculated
Your age in years is the number of full years between your birth date and the chosen date. The calculator then counts the remaining full months and leftover days. Total days are the exact number of calendar days between the two dates, so leap years are handled automatically. Weeks are total days divided by seven and rounded down. Hours are simply days multiplied by 24, because the calculator works with calendar dates rather than the exact time you were born.
Why different age calculators can disagree by a day or two
Months have different lengths, so "1 month and 3 days" depends on how you count across a short month. This calculator borrows days from the month before the end date, which is the most common method. Total days and total weeks are unaffected, so if you need one exact figure for a form or contract, use the total days.
Leap-day birthdays
People born on February 29 have a true birthday only once every four years. In non-leap years this calculator counts the next birthday as March 1, which is how many legal systems treat it, though rules differ by country and by purpose. Check local rules if the exact date matters for something like eligibility.
Handy uses
- Checking age eligibility for a school, sport, license or program
- Counting how many days old a child or pet is
- Planning a milestone birthday
- Finding your age on a past or future date by changing the "age on" field