Age Calculator
Enter a date of birth to see the exact age in years, months and days, today or on any date you choose, plus total days lived and how long until the next birthday.
Dates are calculated inside your browser and are not sent to our server.
How to use the Age Calculator
- Enter the date of birth. On most phones a date picker opens; on a computer you can also type the date.
- Leave Age on this date set to today, or change it to find an age on a past or future date, such as a school cut-off or a retirement date.
- Read the exact age in years, months and days, the totals, and the countdown to the next birthday.
- If the birthday is February 29, choose whether it counts on February 28 or March 1 in non-leap years.
How the age is counted
The calculator counts whole years first: a year is complete on each birthday. It then counts whole months from the last birthday, and finally the days left over. Someone born on May 15, 1990 is 36 years, 4 months and 19 days old on October 4, 2026: four months take you from May 15 to September 15, and 19 more days reach October 4.
Months have different lengths, so one rule needs explaining. When the birth day does not exist in a later month, the month is treated as complete on that month's last day. A baby born on January 31 is one month old on February 28 (or February 29 in a leap year), not on March 3. Other calculators sometimes handle this case differently, so a result of "1 month 1 day" versus "1 month 3 days" can depend on the convention.
Totals are exact counts of calendar days between the two dates using the Gregorian calendar, including every leap day. The calculation works on the dates themselves rather than on clock times, so time zones and daylight-saving changes cannot shift the answer by a day.
Leap-day birthdays
People born on February 29 only see their exact birthday every four years or so (century years are leap years only when divisible by 400, so 1900 was not and 2000 was). In the years between, some celebrate on February 28 and some on March 1, and rules for legal age can differ between places and purposes. The calculator lets you pick either day, and both the age and the birthday countdown follow your choice. If a legal deadline depends on it, check the rule that applies to you.
Frequently asked questions
Does the calculator include leap years?
Yes. It uses the full Gregorian leap-year rule (every fourth year, except century years not divisible by 400), so total days and day-of-week names are correct for any date from the year 100 onward.
Can I calculate an age on a date in the future?
Yes. Change "Age on this date" to any later date. That is handy for checking how old someone will be on a cut-off date for school, a competition or an application.
Why does the countdown say a different number than another site?
Usually because of the time of day. This tool counts calendar days from the date you entered, not hours from right now, so the countdown to tomorrow is always 1 day. Sites that count hours can be off by one.
How are total weeks shown?
As full weeks plus any leftover days. 10,000 days, for example, is 1,428 weeks and 4 days.
Is the date of birth stored?
No. Everything is worked out in your browser. Nothing is sent to us or saved after you close the page.