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.

Wie alt ist jemand, geboren 2009? Altersrechner

Your date of birth

Date of birth

Calculate age as of

Also show Korean age

Results

Total days: 6,296
Total weeks: 899
Total months: 206
Total hours: 151,104
Seconds lived: 0

2009 age range (2026)

	Alter
Alter nach dem Geburtstag (frühestes Datum im Jahr)	17
Alter vor dem Geburtstag (spätestes Datum im Jahr)	16

Browse 2009 by month

january 2009 february 2009 march 2009 april 2009 may 2009 june 2009 july 2009 august 2009 september 2009 october 2009 november 2009 december 2009

Example dates in 2009

Geburtsdatum	Aktuelles Alter	Calculator
1. Januar 2009	17	Open
15. Juni 2009	17	Open
10. September 2009	17	Open
31. Dezember 2009	16	Open

All dates in 2009 (sample)

Date	Page
1. Januar 2009	january-1-2009
15. Januar 2009	january-15-2009
31. Januar 2009	january-31-2009
1. Februar 2009	february-1-2009
15. Februar 2009	february-15-2009
28. Februar 2009	february-28-2009
1. März 2009	march-1-2009
15. März 2009	march-15-2009
31. März 2009	march-31-2009
1. April 2009	april-1-2009
15. April 2009	april-15-2009
30. April 2009	april-30-2009
1. Mai 2009	may-1-2009
15. Mai 2009	may-15-2009
31. Mai 2009	may-31-2009
1. Juni 2009	june-1-2009
15. Juni 2009	june-15-2009
30. Juni 2009	june-30-2009
1. Juli 2009	july-1-2009
15. Juli 2009	july-15-2009
31. Juli 2009	july-31-2009
1. August 2009	august-1-2009
15. August 2009	august-15-2009
31. August 2009	august-31-2009
1. September 2009	september-1-2009
15. September 2009	september-15-2009
30. September 2009	september-30-2009
1. Oktober 2009	october-1-2009
15. Oktober 2009	october-15-2009
31. Oktober 2009	october-31-2009
1. November 2009	november-1-2009
15. November 2009	november-15-2009
30. November 2009	november-30-2009
1. Dezember 2009	december-1-2009
15. Dezember 2009	december-15-2009
31. Dezember 2009	december-31-2009

Altersmeilensteine

Alter	Jahr erreicht
16	2025
18	2027
21	2030
25	2034
30	2039

So wird berechnet

Das Kalenderalter zählt vollendete Geburtstage. Grob: Referenzjahr minus Geburtsjahr, minus 1 wenn der Geburtstag noch aussteht.
Genaues Alter = Jahre + Monate + Tage zwischen Geburts- und Referenzdatum, mit korrekter Monatslänge.

Age = Reference date − Birth date

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

Nahe Geburtsjahre

2007 2008 2009 2010 2011