This age calculator determines a person's age on a selected date in completed years, months, and days. It also reports total days lived and the next birthday, making it useful for forms, records, and personal planning.
How to use this calculator
Enter the birth date and the date on which you want to know the age. The target defaults to today when the page loads. Completed calendar units are used rather than dividing total days by an average year length.
Formula & calculation method
Age = completed calendar years + remaining completed months + remaining daysThe calculation first counts full years, then full calendar months, and finally remaining days. Total days uses the difference between calendar dates. The next birthday is found in the target year or the following year if this year's birthday has passed.
Worked example
Someone born on 15 June 2000 is 24 years, 4 months, and 2 days old on 17 June 2024. A different target date can be selected for historical records or a future eligibility check.
Why this is useful
Calendar-based results avoid the inaccuracies of assuming every year has 365 days or every month has 30 days. Multiple formats make the output useful for both precise records and an intuitive understanding of age.
Limitations to keep in mind
The calculator uses the calendar dates supplied by the browser and does not infer a birth time or time zone. Legal age rules can depend on jurisdiction and time of birth, so official requirements should be checked separately.
Frequently asked questions
How are leap birthdays handled?
Chronological age still advances by elapsed calendar time. For an unofficial next-birthday display in a non-leap year, February 29 is observed on February 28 in this tool; legal conventions may differ.
Can I calculate age on a past date?
Yes. Choose any target date on or after the birth date to calculate the completed age at that time.
Does total days include the birth date?
No. It measures elapsed 24-hour calendar-day boundaries from the birth date to the target date, excluding the starting day.