Free online age calculator. Enter your date of birth to calculate the exact age in years, months, and days. Also find out the total days lived, weeks, next birthday countdown, day of birth, and zodiac sign.
The exact age is:
Age in years:
Age in months:
Age in weeks:
Age in days:
Day of birth:
Next birthday:
Zodiac sign:
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Enter the date of birth and an as-of date (today or another day) and press Calculate age. The main result is calendar years, months, and days.
This calculator's main result —years, months, and days— is not obtained by dividing the total number of days by 365. It subtracts the civil calendar: first it counts the full years up to the last birthday, then the full months from that date to the same day of the as-of month and, finally, the days that remain. The year count only increases on the birthday, not on January 1.
An example: if the date of birth is May 7, 2000 and the as-of date is August 17, 2026, from May 7, 2000 to May 7, 2026 26 years have already been completed. From that birthday to August 7 there are 3 full months. Finally, from August 7 to August 17, 10 days remain. The exact age is therefore 26 years, 3 months, and 10 days.
Chronological age is the time elapsed from the date of birth to today, or to another as-of date. It is expressed in calendar years, months, and days: the usual way to say how old a person is. This calculator returns that age, not an estimate of physical condition or biological aging.
In Excel you can get the same breakdown as this calculator by putting years, months, and days in separate cells. Put the date of birth in A2 and the as-of date in B2. If you are measuring as of today, replace B2 with TODAY().
Completed years run from birth to the last birthday before the as-of date. In Excel they are calculated by the DATEDIF function with the unit "Y": =DATEDIF(A2, B2, "Y"). The number only increases on the birthday, just as on this page.
Remaining months are those after that birthday and before the as-of date: a value between 0 and 11. DATEDIF returns them with the unit "YM", which ignores the years and leaves only those months: =DATEDIF(A2, B2, "YM"). In the May 7 to August 17 example, this result is 3.
Remaining days run from the same day of the month as the birthday to the as-of date. If that day has not yet arrived, Excel borrows the days of the previous month. If the result is negative (born on the 31st, with February in between), this page keeps subtracting the previous month. One way to write it is: =IF(DAY(B2)>=DAY(A2), DAY(B2)-DAY(A2), DAY(DATE(YEAR(B2), MONTH(B2), 0))+DAY(B2)-DAY(A2)).
DATEDIF also accepts the unit "MD" for this same figure, but Microsoft documents that it can return an incorrect result. That is why we do not use it here.
Chronological age is the same for everyone with the same date of birth: it counts calendar time. Biological age tries to describe wear on the body and can vary with genetics and habits, so two people with the same chronological age need not “look” equally old. This tool does not calculate biological age; it only measures the time between the two dates.
Change the as-of date: the calculator returns the exact chronological age on that day, not today’s. Use it when a form asks for age as of 1 January, exam day, a contract date, or a date of death.
The cutoff date is not a detail: someone can be 17 today and 18 on the day that matters for the form. The year count only increases on the birthday (on the civil calendar), not on 1 January.
The result at the top (years, months, and days) is civil age: completed years to the last birthday, plus leftover months and days. The Age in years, in months, in weeks, and in days figures start from the total number of elapsed days; they are not the same clock.
Total days counts every calendar day between the two dates, including 29 February. The years and months in that box divide those days by 365.25 and 30.4375 (Gregorian averages) and show one decimal. That is why you can see 26 years, 3 months, and 10 days above and 26.3 under “Age in years”.
That total in months is not the pediatric count (years × 12 + completed months). If a protocol asks for completed months, use the civil breakdown at the top, not the decimal in the box.
In a common (non-leap) year, this calculator treats the birthday as 1 March. 28 February does not yet add a year; 1 March does.
Example: born on 29 February 2020, on 28 February 2025 this page has not yet turned age 5; on 1 March 2025 it has. The “next birthday” countdown follows the same rule when the as-of year has no 29 February.
Other calculators and some procedures use 28 February in common years. One day can move a deadline. If the form does not state the rule, ask the authority: here the convention is 1 March, and it is written down.
Chronological age counts from the day of birth. Corrected (or adjusted) age subtracts the weeks of prematurity, as if birth had been at 40 weeks. This calculator only returns chronological age.
Pediatrics uses both clocks: growth charts often use corrected age for the first 2 or 3 years; immunization schedules generally follow chronological age. That is not a contradiction: they are different rules. Corrected age needs gestational age; that step is not in this form and does not replace clinical judgment.
Yes. The tool does not distinguish “your” date from someone else’s: any date of birth and any as-of date work. It can be used for a child, a parent, or a historical figure.
No. The calculation runs in your browser. The date is not sent to a server and is not kept when you close or reload the page.
In non-leap years this page counts the birthday as 1 March. 28 February does not yet add a year. The explanation is in the section on 29 February.
Yes. Put that date in As-of date and leave the date of birth. You get the exact chronological age on that day, in the past or the future.
No. Here the result is a civil age (years completed on the birthday). A day counter measures an interval and often includes both end dates, so it can differ by one day. If you need how many days lie between two dates, use the Day Counter.