Age Calculator
This free age calculator tells you exactly how old you are, down to the year, month, and day, from any date of birth. Beyond your current age, it shows the total number of days and weeks you've lived and counts down to your next birthday. You can also calculate age as of any date, past or future, not just today.
How to Use It
- Enter your date of birth in the first set of fields.
- Your current age, total days lived, total weeks lived, and next birthday appear instantly.
- To calculate age on a different date, change the "Age as of" fields, which default to today.
- Update either date at any time, and the results recalculate live.
How It Works
This calculator works by comparing two calendar dates, your date of birth and a reference date (today, by default), and counting the whole years, months, and days between them. It doesn't simply divide the number of days lived by 365, since that would drift out of sync with real calendar years thanks to leap years. Instead, it walks the calendar the way you would by hand: counting full years first, then the remaining full months, then the remaining days.
For the "total days lived" and "total weeks lived" figures, it counts every calendar day between the two dates, including leap days. For the next-birthday countdown, it finds your birthday in the current year and, if that date has already passed, moves the countdown to your birthday next year instead, so the countdown is always to your next birthday, never a past one.
A worked example: someone born March 15, 1994, calculating their age as of July 27, 2026, comes out to 32 years, 4 months, 12 days: 11,822 total days lived, 1,688 total weeks, and 231 days until their next birthday. The years/months/days breakdown and the total-days count are two genuinely different calculations run on the same two dates, which is why they're shown side by side rather than one being derived from the other.
Everything runs client-side in your browser. No dates you enter are sent anywhere or stored.
Frequently Asked Questions
How does this calculator handle leap years?
Leap years are accounted for automatically using the calendar's actual rules (a year is a leap year if it's divisible by 4, except centuries not divisible by 400). If you were born on February 29th, this calculator treats March 1st as your birthday in non-leap years, so your age and next-birthday countdown stay consistent every year.
How is age calculated for people born on February 29?
Since February 29 only exists in leap years, this calculator counts your age as turning over on March 1 in years without a February 29. This is one of the more common conventions, though some legal contexts use February 28 instead. Either way, your age changes by exactly one year, once a year.
Are age calculation conventions the same everywhere?
Not always. Most Western countries count age as the number of full years since birth, which is what this tool calculates. Some cultures use different conventions historically. For example, traditional East Asian age reckoning could count a person as one year old at birth. This calculator uses the standard full-years-elapsed method.
Can I calculate my age on a date other than today?
Yes. The "Age as of" field defaults to today, but you can change it to any date, past or future, to see your exact age as of that day, along with the next-birthday countdown from that reference point.
Why does "total days lived" not exactly match my age in years times 365?
Because a plain years-times-365 estimate ignores leap days entirely. Someone born March 15, 1994 is 32 years, 4 months, and 12 days old as of July 27, 2026, a total of 11,822 actual calendar days, which works out to about 365.25 days per year on average once every leap day since 1994 is counted, not a flat 365.
Does my time zone affect the result?
No. This calculator compares calendar dates directly (year, month, day) rather than exact timestamps, so it isn't affected by which time zone you or your device are set to. Your age comes out the same whether you calculate it from New York or Tokyo, as long as the date of birth you enter is correct.
How many weeks old is that in total?
Total weeks lived is just total days lived divided by 7, rounded down to a whole week. Using the same example above (11,822 total days), that comes to 1,688 full weeks, a popular way some people find seeing their lifespan "in weeks" puts a long time span into a more concrete, countable number.