Age Calculator

Age is counted in complete units. First the whole years since your date of birth, then the whole months since your last birthday, then the days left over. A partial month is never rounded up; it stays as days.

For example, someone born on March 14, 1990 is 36 years, 7 months and 15 days old on October 29, 2026: 36 years to March 14, 2026, 7 more months to October 14, then 15 days.

The totals count every calendar day you have lived, leap days included. Total weeks is the day count divided by 7, and total hours is 24 for each of those days, because the time of birth isn't part of the input.

Months are not all the same length, so a birthday on the 29th, 30th or 31st needs a rule. When a month has no matching day, this calculator counts the anniversary on that month's last day. Someone born on January 31 is exactly 1 month old on February 28 (February 29 in a leap year), and 1 month and 1 day old on March 1.

The same rule covers leap-day birthdays. If you were born on February 29, your birthday counts on February 28 in years without a February 29, so you turn 18 on February 28 of a common year. Legal rules vary by country, and some treat March 1 as the anniversary instead. The result also shows how many real February 29 birthdays you have had and when the next one is.

Choose Another date under “Age on” to see how old someone was on a date in the past, or how old they will be on one in the future: a wedding, a graduation, a passport renewal or the year 2050. The countdown then runs to the next birthday after that date.

The answer depends only on the two calendar dates you pick. It uses the date on your own device for “today” and plain calendar arithmetic for everything else, so it comes out the same in every time zone. The full set of rules is written out in the calculation methodology.

Only know an age, not a date? The birth year calculator works out the year someone was born. For an age written as years;months.days on a test record form, use the chronological age calculator for testing.