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 in 2021? Age Calculator

Your date of birth

Date of birth

Calculate age as of

Also show Korean age

Results

Total days: 1,913
Total weeks: 273
Total months: 62
Total hours: 45,912
Seconds lived: 0

2021 age range (2026)

	Age
Age after birthday (earliest DOB in year)	5
Age before birthday (latest DOB in year)	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

Birth date	Current age	Calculator
January 1, 2021	5	Open
June 15, 2021	5	Open
September 10, 2021	5	Open
December 31, 2021	4	Open

All dates in 2021 (sample)

Date	Page
January 1, 2021	january-1-2021
January 15, 2021	january-15-2021
January 31, 2021	january-31-2021
February 1, 2021	february-1-2021
February 15, 2021	february-15-2021
February 28, 2021	february-28-2021
March 1, 2021	march-1-2021
March 15, 2021	march-15-2021
March 31, 2021	march-31-2021
April 1, 2021	april-1-2021
April 15, 2021	april-15-2021
April 30, 2021	april-30-2021
May 1, 2021	may-1-2021
May 15, 2021	may-15-2021
May 31, 2021	may-31-2021
June 1, 2021	june-1-2021
June 15, 2021	june-15-2021
June 30, 2021	june-30-2021
July 1, 2021	july-1-2021
July 15, 2021	july-15-2021
July 31, 2021	july-31-2021
August 1, 2021	august-1-2021
August 15, 2021	august-15-2021
August 31, 2021	august-31-2021
September 1, 2021	september-1-2021
September 15, 2021	september-15-2021
September 30, 2021	september-30-2021
October 1, 2021	october-1-2021
October 15, 2021	october-15-2021
October 31, 2021	october-31-2021
November 1, 2021	november-1-2021
November 15, 2021	november-15-2021
November 30, 2021	november-30-2021
December 1, 2021	december-1-2021
December 15, 2021	december-15-2021
December 31, 2021	december-31-2021

Age milestones

Age	Year reached
5	2026
10	2031
13	2034
16	2037
18	2039

How this is calculated

Calendar age in years counts completed birthdays. A quick estimate is reference year minus birth year, then subtract 1 if the birthday has not yet occurred in the reference year.
Exact age = years + months + days between birth date and reference date, borrowing days from the previous month when needed.

Age = Reference date − Birth date

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

Nearby birth years

2019 2020 2021 2022 2023