Age Calculator
Find your exact age in years, months, and days — plus how long until your next birthday.
How to Calculate Your Age
- Enter your date of birth in the "Date of Birth" field.
- The "As Of" field defaults to today's date — change it if you want your age calculated as of a different date.
- Click "Calculate Age" to see your age broken into years, months, and days.
- Check the stats row for your total number of days lived and how many days remain until your next birthday.
Frequently Asked Questions
How does the calculator handle months with different numbers of days?
When counting months and days, if the as-of day of the month falls before your birth day of the month, the tool borrows the number of days in the previous calendar month, so the day count is always accurate rather than assuming a flat 30 days.
Why would I change the As Of date instead of using today?
Setting a custom as-of date lets you calculate someone's age on a past or future date — useful for eligibility checks, legal documents, or figuring out how old you were on a specific historical date.
How is Days to Next Birthday calculated?
The tool finds your birth month and day in the current (or next) year, and if that date has already passed relative to the as-of date, it rolls forward to next year — then counts the days remaining.
What happens if I enter a birth date that's after the As Of date?
The calculator shows an error asking you to make sure the date of birth comes before the as-of date, since a negative age isn't meaningful.
Does Total Days Lived account for leap years?
Yes — it's calculated directly from the millisecond difference between the two dates, so every leap year's extra day is automatically included without any special-case logic.