Start with the counting method
The phrase “Korean age” can refer to traditional counting, while official or administrative uses may follow other rules. Our cultural calculator shows three values together. This makes the difference visible without requiring you to change the birth date between calculations.
Traditional age
Traditional counting assigns one year at birth and increases the number on 1 January. The formula is reference year minus birth year plus one. Because the increase is tied to the new calendar year, two people born in the same year receive the same traditional age on a given reference date.
For a person born on 20 December 2000, the traditional result on 5 November 2026 is 27. That comes from 2026 minus 2000 plus one. Their birthday has no part in that arithmetic once the birth year is known.
International age
International age counts completed years since the actual birth date. In the same example, the person is 25 on 5 November 2026 because the December birthday has not arrived. They turn 26 on 20 December. The traditional and international values can therefore differ by one or two.
Year age
The year-age value is reference year minus birth year. For the example above, it is 26. It treats everyone born in 2000 as reaching that value in 2026, without checking whether the birthday has passed. It is displayed as a separate value because it is easy to confuse with either of the other two systems.
Use the appropriate rule for official tasks
South Korea's amendments introducing international age as the general civil and administrative standard took effect on 28 June 2023. The traditional result on this site remains useful for understanding cultural counting. A particular activity or institution can have specific requirements, so consult the organisation's instructions for an application or eligibility decision.
The source for the effective date is the Ministry of Justice announcement. Our calculator uses a Gregorian birth date and reference date. It does not convert lunar birthdays or calculate other cultural age systems. If you need an ordinary age on a form's cutoff date, use the main age calculator and select that cutoff as the reference date.