Age calculator

Completed years of age from a birth date and today on your device, the Korean international-age rule. Feb 29 births advance on March 1 in common years.

Result—

What to know

This page returns age in completed years, the count that Korea calls man-nai and that most countries use. The formula is years = todayYear - birthYear, minus 1 if today falls before the birthday in the current year, where the comparison looks at month first and day second.

A worked example: born 1990-06-15, the age is 34 on 2025-06-14 and 35 on 2025-06-15. Nothing changes on 1 January, which is why the result differs from the year-based age (current year minus birth year) and from the counting age that starts at 1 and adds a year on New Year.

Birthdays on 29 February have no match in common years, so the check says the birthday has not arrived until 1 March. A person born 2000-02-29 reads 24 on 2025-02-28 and 25 on 2025-03-01. Legal conventions for leap-day births can differ, so check the rule that your authority applies.

The birth date cannot be later than today, and the page flags it if it is. The result is shown as a number plus the word for years, using the date on your device.

In Korea the completed-year count is the standard in administrative and legal use, while the year-based age (current year minus birth year) still appears in some age-limit rules such as school entry or alcohol and tobacco sales. Check which count your rule uses.

Choose a specific task 8
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How to use Age calculator
  1. Enter Birth date 1990-06-15.
  2. Let the device supply today, for example 2025-06-14.
  3. Read the Result line, which shows 34 years old.
  4. Move the device day to 2025-06-15 or later and the result becomes 35.

Quick answers

How is this different from the year-based age?

The year-based age is simply current year minus birth year, so someone born on 1990-12-31 is already 35 on 2025-01-01. This page waits for the birthday.

When does a 29 February birthday add a year?

On 1 March in years without a leap day, because the page compares month and day numbers. In a leap year it advances on 29 February itself.

What happens with a birth date in the future?

The page rejects it with a message that the birth date cannot be after today, and shows no age.

Does the age count months or days beyond whole years?

No. It only returns whole years. For days, use the days-lived page.