Age Calculator
Calculate exact age in years, months, and days, plus fun birthday facts.
What the Age Calculator does
This Age Calculator works out an exact age from a date of birth and a reference date. Instead of giving only a rounded number of years, it breaks the result down into completed years, months, and days, so you can see precisely how old someone is on any given day.
It is handy for filling in forms that ask for an exact age, settling friendly debates about who is older, planning milestone birthdays, or simply satisfying curiosity. Because you can change the "As of" date to any day in the past or future, you can also project how old someone will be on a particular occasion.
How to use it
Pick the date of birth in the first field. By default the second "As of" field is set to today, but you can change it to any date, or click "Use today" to reset it back to the current date.
The calculator updates instantly as you change either date. Alongside the exact age it shows the total number of days lived, an approximate count of hours lived, the day of the week the person was born, and how many days remain until the next birthday.
How the calculation works
Age is calculated by comparing calendar components rather than simply dividing the total number of days. The tool subtracts the birth month and day from the reference month and day, borrowing from the previous month or year when needed, which means leap years and months of different lengths are handled correctly.
The day-of-week figure is derived from the birth date itself, and the days-until-next-birthday value rolls forward to next year automatically once this year's birthday has already passed. Every figure is recomputed in your browser, so the numbers stay accurate even for dates far in the past or future.