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.

Born in May 2009? Age Calculator

31 dates in May 2009
Birth date	Age today (years)	Page
May 1, 2009	17	Calculate
May 2, 2009	17	Calculate
May 3, 2009	17	Calculate
May 4, 2009	17	Calculate
May 5, 2009	17	Calculate
May 6, 2009	17	Calculate
May 7, 2009	17	Calculate
May 8, 2009	17	Calculate
May 9, 2009	17	Calculate
May 10, 2009	17	Calculate
May 11, 2009	17	Calculate
May 12, 2009	17	Calculate
May 13, 2009	17	Calculate
May 14, 2009	17	Calculate
May 15, 2009	17	Calculate
May 16, 2009	17	Calculate
May 17, 2009	17	Calculate
May 18, 2009	17	Calculate
May 19, 2009	17	Calculate
May 20, 2009	17	Calculate
May 21, 2009	17	Calculate
May 22, 2009	17	Calculate
May 23, 2009	17	Calculate
May 24, 2009	17	Calculate
May 25, 2009	17	Calculate
May 26, 2009	17	Calculate
May 27, 2009	17	Calculate
May 28, 2009	17	Calculate
May 29, 2009	17	Calculate
May 30, 2009	17	Calculate
May 31, 2009	17	Calculate

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Born in May 2009: Age Calculator