How the age calculator works
The calculator counts the whole years and months between the two dates, then the remaining days. It handles month lengths and leap years correctly. When a birthday falls on a day that does not exist in a given month — such as the 31st, or February 29 in a non-leap year — that month is treated as complete on its last day. It also reports the total days, weeks and months you have been alive and how many days remain until your next birthday.
The method
First, count the number of full months from the birth date to the "as of" date, without passing it. Twelve months make a year. Then count the days from that last monthly anniversary to the target date. Total days are simply the calendar days between the two dates.
Example
Someone born on December 30, 1981 is 44 years, 9 months and 22 days old on October 22, 2026: 44 years brings us to December 30, 2025, nine more months to September 30, 2026, and 22 days to October 22. Their next birthday is 69 days away.
Common uses
An exact age is needed for forms, retirement and Social Security planning, insurance quotes, school enrollment cut-offs and eligibility rules. Many age-based milestones in U.S. finance depend on specific birthdays, such as catch-up retirement contributions starting in the year you turn 50, penalty-free IRA withdrawals after age 59½, and required minimum distributions later in life. You can also set the "as of" date to the future to see how old you will be on a particular day.
Frequently asked questions
How is age calculated for someone born on February 29?
In non-leap years this calculator treats February 28 as the anniversary when counting full years. Some legal systems use March 1 instead.
Does the calculator use my time zone?
It uses calendar dates only, so the time of day and time zone do not affect the result.
Can I calculate age on a future date?
Yes. Change the "Age as of" date to any date after the birth date.
Why might another site show a different number of days?
Tools handle month-end dates differently, so the months-and-days split can vary by a day. The total number of days lived will always match.
Results are estimates for educational purposes only and are not financial, tax, legal or medical advice. See our disclaimer. Last reviewed 2026-10-22.