One birthday, three numbers. Make sense of international, traditional Korean and calendar age.
Sources reviewed: 2026-10-07 / Event date: 2023-06-28
The official standard changed in 2023
Since June 28, 2023, international age has been the default for civil and administrative matters in South Korea, unless a specific law sets a different rule. Older Korean dramas and fan conversations may still refer to traditional counting age.
International age: birthdays count
Start at zero when you are born. Add one on each birthday. Someone born on December 30, 2000 is 25 on October 7, 2026.
Traditional Korean age: the year counts
Traditionally, a baby starts at one, and everyone adds one on January 1. The formula is current year minus birth year plus one. That same person has a traditional counting age of 27 in 2026. This is a cultural comparison, not the default official age.
Calendar age is a third number
Calendar age is current year minus birth year, without checking the birthday. For that example, it is 26. Specific rules can use a different convention, so a cultural calculator does not determine eligibility for a service.
Sources & further reading
Ministry of Government Legislation: age standardization (Korean)