Age calculator

The calculator first counts whole calendar months from your date of birth to the chosen date, clamping to the last day of shorter months, then counts the remaining days. Years are whole groups of twelve months. Total days are counted on the real calendar, so leap days are included, and the day of birth itself is not counted as a day lived.

In common years the tool treats 28 February as your birthday, so your age goes up on that day and the next-birthday countdown points to 28 February, unless the coming year is a leap year, when it points to 29 February. Some countries and organisations use 1 March instead, so check the rule that applies to you.

If the date you are measuring against is your birthday, the countdown shows Today with that date rather than counting 365 days to the following one. Your age in years already includes the new year, because the calculator treats a birthday as reached at the start of that day.

Yes. Change the "Age on this date" field to any date after your birth, for example the first day of a school year, a retirement date or a historical event, and the tool recalculates instantly. If you pick a date before your birth it shows an error instead of a negative age.

Total days is the number of midnights between your birth date and the chosen date. On the day you were born you are 0 days old, the next day 1 day old, and so on. Multiply by 24 for hours or divide by 7 for weeks; the figure counts every leap day since you were born.