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 2021? Altersrechner

Your date of birth

Date of birth

Calculate age as of

Also show Korean age

Results

Total days: 1,914
Total weeks: 273
Total months: 62
Total hours: 45,936
Seconds lived: 0

2021 age range (2026)

	Alter
Alter nach dem Geburtstag (frühestes Datum im Jahr)	5
Alter vor dem Geburtstag (spätestes Datum im Jahr)	4

Browse 2021 by month

january 2021 february 2021 march 2021 april 2021 may 2021 june 2021 july 2021 august 2021 september 2021 october 2021 november 2021 december 2021

Example dates in 2021

Geburtsdatum	Aktuelles Alter	Calculator
1. Januar 2021	5	Open
15. Juni 2021	5	Open
11. September 2021	5	Open
31. Dezember 2021	4	Open

All dates in 2021 (sample)

Date	Page
1. Januar 2021	january-1-2021
15. Januar 2021	january-15-2021
31. Januar 2021	january-31-2021
1. Februar 2021	february-1-2021
15. Februar 2021	february-15-2021
28. Februar 2021	february-28-2021
1. März 2021	march-1-2021
15. März 2021	march-15-2021
31. März 2021	march-31-2021
1. April 2021	april-1-2021
15. April 2021	april-15-2021
30. April 2021	april-30-2021
1. Mai 2021	may-1-2021
15. Mai 2021	may-15-2021
31. Mai 2021	may-31-2021
1. Juni 2021	june-1-2021
15. Juni 2021	june-15-2021
30. Juni 2021	june-30-2021
1. Juli 2021	july-1-2021
15. Juli 2021	july-15-2021
31. Juli 2021	july-31-2021
1. August 2021	august-1-2021
15. August 2021	august-15-2021
31. August 2021	august-31-2021
1. September 2021	september-1-2021
15. September 2021	september-15-2021
30. September 2021	september-30-2021
1. Oktober 2021	october-1-2021
15. Oktober 2021	october-15-2021
31. Oktober 2021	october-31-2021
1. November 2021	november-1-2021
15. November 2021	november-15-2021
30. November 2021	november-30-2021
1. Dezember 2021	december-1-2021
15. Dezember 2021	december-15-2021
31. Dezember 2021	december-31-2021

Altersmeilensteine

Alter	Jahr erreicht
5	2026
10	2031
13	2034
16	2037
18	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

2019 2020 2021 2022 2023