Korean Age Calculator
Enter a birth date below to instantly get Korean age, year age, and international age side by side.
How Korean Age Is Calculated
Korean age (세는 나이) counts a newborn as already 1 year old, then adds 1 to everyone's age at once on January 1st — birth month and day don't matter at all once the birth year is known. Year age (연 나이) uses the same January 1st rule but starts counting from 0 instead of 1. International age (만 나이) is the familiar birthday-based age used almost everywhere else.
Worked example
Born December 31, 2000. As of January 1, 2001 — one day later.
Korean age: 2001 − 2000 + 1 = 2. Year age: 2001 − 2000 = 1. International age: the birthday hasn't arrived a full year yet, so it's 0.
A baby who is one day old is already "2" in Korean age — the most extreme case, since the birth year and the New Year fall on consecutive days.
Frequently Asked Questions
Why is Korean age different from international age?
Korean age (세는 나이, "counting age") counts a newborn as already 1 year old, and everyone gains a year together on January 1st regardless of birth date — not on their individual birthday. International age (만 나이) starts at 0 and only advances on the person's own birthday, the system almost everywhere else in the world uses.
How much older is Korean age than international age?
Usually 1 or 2 years older, depending on whether the birthday has already happened this year. If the birthday already passed this year, Korean age is exactly 1 more than international age. If it hasn't happened yet, Korean age is 2 more.
Does Korean age use the lunar calendar?
No — despite the traditional East Asian calendar's association with Lunar New Year, modern Korean age counting uses the Gregorian January 1st as the day everyone's age increases, not the Lunar New Year date.
Is Korean age still used officially in South Korea?
No. South Korea officially adopted international age (만 나이) for all legal and administrative purposes starting June 28, 2023. Korean age is still used casually in everyday conversation and in media, which is why the gap between someone's Korean age and international age still comes up.
What is "year age" (연 나이)?
Year age is a third, less common system: it counts the same way as Korean age — everyone's age changes together on January 1st — but starts at 0 at birth instead of 1. It was used in a handful of Korean laws (like enlistment age) even before the 2023 international-age reform.
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