How this calculator works
Traditional Korean age counts the calendar year you were born in as one full year, then adds a year on every January 1. Everyone born in the same year therefore has the same Korean age. International age, by contrast, adds a year only on the birthday. Year age is the simple subtraction of birth year from the current year, without the extra first year.
Formula
Traditional Korean age = reference year - birth year + 1. Year age = reference year - birth year. International age = reference year - birth year, minus one if the birthday has not yet occurred in the reference year.
Worked example
Born on 1990-05-20 and measured on 2026-11-01: international age is 36, traditional Korean age is 37, and year age is 36. In January 2026, before the birthday, international age would have been 35 while Korean age was already 37.
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Frequently asked questions
Is Korean age still used in South Korea?
Not for official purposes. On 28 June 2023 South Korea amended the Civil Act and related laws so that international age applies in legal and administrative contexts. The traditional count is still used socially by some people, especially older generations.
Why can the difference be two years?
Traditional age gains a year on January 1, while international age gains one on the birthday. For someone whose birthday is later in the year, the gap before that birthday is two years; after it, the gap is one year.
Does the Korean lunar calendar matter here?
Historically the count followed the lunar year, so the New Year boundary could fall in late January or February. This page uses the Gregorian year as the current legal and everyday basis. Around the lunar New Year the traditional count can differ by one.
What is year age used for?
Some Korean laws and school rules use a year-based age, which counts birth year rather than birthday. It is also the basis from which traditional age adds one. The page shows it separately so the three numbers are easy to compare.