How to use the Age Calculator
- Enter a date of birth.
- Leave 'Age on' as today, or pick another date to find an age in the past or future.
- Read the exact age, total days and weeks, and the countdown to the next birthday.
How it works
The calculator counts full years first, then full months, then the remaining days. If the birth day hasn't come yet in the current month, it borrows the days of the previous month, the same way you would count on a calendar.
For people born on February 29, the next-birthday countdown uses March 1 in years that are not leap years. Legal rules for this differ between countries.
Formula
Age = full years + full months + remaining days between the two dates
Example
Someone born on March 17, 1994 is 32 years, 7 months and 3 days old on October 20, 2026. That is 11,905 days, or about 1,700 weeks.
Where exact age matters
- Forms and applications. Many forms ask for age on a set date, such as age on January 1 for school entry or sports age groups. Change the "Age on" date to match.
- Retirement and benefits. Eligibility often depends on reaching an exact age, such as 65. Find the date by entering a future "Age on" date.
- Milestones. See when you or a child will be 10,000 days old, or how many weeks old a baby is.
Why months have different lengths
Because months have 28 to 31 days, "months and days" depends on the calendar. From January 31 to March 1, for example, is 1 month and 1 day in a non-leap year. The calculator follows the same calendar counting that people use by hand, so its answer matches what you would count on a wall calendar.
Frequently asked questions
How do I work out my age in months?
Multiply your full years by 12 and add the extra months. At 32 years and 7 months you are 391 months old.
Can I find someone's age on a past date?
Yes. Change the 'Age on' date to any day after the birth date.
How many days old am I?
Enter your birth date and read 'In days'. It counts every day from your birth date up to the 'Age on' date.
How is a February 29 birthday handled?
In non-leap years the next-birthday countdown uses March 1.
Last reviewed October 20, 2026. Spotted an error? Tell us.