How do I calculate my age from my date of birth?

Subtract your birth year from the current year. If your birthday has not happened yet this year, subtract one more year from that total. Then count the months and days separately using the same subtract-and-borrow method. This tool does all of that automatically. You just get the finished answer.

Can I calculate my age on a specific date?

Yes. Instead of leaving the calculate-as-of field on today, pick any date, past or future, and the tool works out your age as of that day. Use this for school enrollment cutoffs, immigration age requirements, or figuring out how old you will be on a future date like a wedding or retirement.

How does this handle leap years?

Leap years are built into the calendar math, not added as an afterthought. If someone's birthday is February 29, this tool treats it as February 28 in non-leap years for counting elapsed years, the same convention most legal and administrative systems use, while still calculating the exact day count correctly underneath.

What is chronological age?

Chronological age is the time that has passed since birth, measured in the calendar: years, months, and days. It is different from biological age, which estimates how old a body seems rather than how long a person has actually been alive. When a form or a doctor asks for your age, chronological age is what they mean.

How is Korean age different from international age?

Korean age starts at one, not zero, on the day someone is born, and everyone's age increases together on New Year's Day instead of on individual birthdays. Depending on birth month, that can put Korean age one or two years ahead of the international age most of the world uses. Toggle Also show Korean age to see both numbers at once.

How do I calculate age difference between two people?

Switch to the Age Difference tab, enter both birth dates, and the calculator returns the gap as years, months, and days, plus a flat day count if you need one number instead of three. It works the same way whether the gap is a few months or several decades.

How accurate is this online tool?

It is accurate to the day, using real calendar date math rather than a simplified days-divided-by-365 estimate. Leap years, varying month lengths, and the borrow-a-month logic are all handled correctly. The one thing it cannot account for is a wrong birth date typed in.

How do I calculate age in Excel?

Put the birth date in a cell, then wrap it in Excel's DATEDIF function with "Y", "YM", and "MD" as the unit arguments to pull out years, months, and days separately. The full formula is in the Excel section above. It is the same calendar-based approach this tool uses, just typed out manually.

Yes. Everything runs in your browser using JavaScript. Your birth date never leaves your device. There are no servers processing your information and no account required. You can disconnect from the internet after loading the page and the calculator still works.

Can I use this for my pet?

Yes. Click the Pet Age tab, choose dog or cat, and enter how many years old your pet is. The tool converts to human-equivalent age using the standard veterinary formula, not the old seven dog years equals one human year shortcut.

How Old Is Someone Born on September 11, 1927?

Current age

99 years

Total days: 36,160
Total weeks: 5,165
Completed months: 1,188
Total hours: 867,840
Total minutes: 52,070,400
Total seconds (live): 3,124,224,000

Next birthday: September 11, 2027 (365 days, turning 100)

Your date of birth

Date of birth

Calculate age as of

Also show Korean age

Results

Total days: 36,160
Total weeks: 5,165
Total months: 1,188
Total hours: 867,840
Seconds lived: 0

Elapsed time

Unit	As of September 11, 2026
Years, months, days	99 years
Total days	36,160
Total weeks (days ÷ 7)	5,165
Total hours	867,840
Total minutes	52,070,400
Total seconds (at page load)	3,124,224,000

Age milestones

Age	Date reached	Day of week
1	September 11, 1928	Tuesday
5	September 11, 1932	Sunday
10	September 11, 1937	Saturday
13	September 11, 1940	Wednesday
16	September 11, 1943	Saturday
18	September 11, 1945	Tuesday
21	September 11, 1948	Saturday
25	September 11, 1952	Thursday
30	September 11, 1957	Wednesday
40	September 11, 1967	Monday
50	September 11, 1977	Sunday
60	September 11, 1987	Friday
65	September 11, 1992	Friday
70	September 11, 1997	Thursday
80	September 11, 2007	Tuesday
90	September 11, 2017	Monday
100	September 11, 2027	Saturday

Reference dates

Date	Exact age
Birth date (Sunday)	0 years, 0 months, 0 days
September 11, 2026	99 years
September 11, 2027	Turning 100
+1 mo → October 11, 2026	99 years, 1 month
+3 mo → December 11, 2026	99 years, 3 months
+6 mo → March 11, 2027	99 years, 6 months
+9 mo → June 11, 2027	99 years, 9 months
+12 mo → September 11, 2027	100 years

Week milestones from birth

Weeks after birth	Date
1	September 18, 1927
4	October 9, 1927
8	November 6, 1927
13	December 11, 1927
26	March 11, 1928
52	September 9, 1928

Related birth dates

50 related calculations
Birth date	Age today	Page
1927-09-10	99	View
1927-09-12	98	View
1927-09-09	99	View
1927-09-13	98	View
1927-09-08	99	View
1927-09-14	98	View
1927-09-04	99	View
1927-09-18	98	View
1927-08-28	99	View
1927-09-25	98	View
1927-08-12	99	View
1927-10-11	98	View
1927-07-13	99	View
1927-11-10	98	View
1927-06-13	99	View
1927-12-10	98	View
1926-09-11	100	View
1928-09-11	98	View
1929-09-11	97	View
1930-09-11	96	View
1931-09-11	95	View
1932-09-11	94	View
1933-09-11	93	View
1934-09-11	92	View
1935-09-11	91	View
1936-09-11	90	View
1937-09-11	89	View
1927-09-01	99	View
1927-09-02	99	View
1927-09-03	99	View
1927-09-05	99	View
1927-09-06	99	View
1927-09-07	99	View
1927-09-15	98	View
1927-09-16	98	View
1927-09-17	98	View
1927-09-19	98	View
1927-09-20	98	View
1927-09-21	98	View
1927-09-22	98	View
1927-09-23	98	View
1927-09-24	98	View
1927-09-26	98	View
1927-09-27	98	View
1927-09-28	98	View
1927-09-29	98	View
1927-09-30	98	View
1927-07-11	99	View
1927-08-11	99	View
1927-11-11	98	View

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How this is calculated

Exact age counts completed calendar years, months, and days between the birth date and the reference date.
Total days is the count of calendar days elapsed between those dates (including leap days).

Age = Reference date − Birth date

Weeks ≈ total days ÷ 7. Hours = total days × 24. Minutes = total hours × 60 (exact for whole-day spans).