Korean Age Calculator

About Korean age systems

Korea traditionally used two age-counting systems that differ from the international standard: "counting age" (se-nai), where everyone is born at age 1 and gains a year every New Year's Day regardless of birthday, and "year age" (yeon-nai), based on the calendar year gap alone. Since June 2023, South Korean law standardized on the international age (man-nai) — the familiar system that counts full years lived since birth — for virtually all legal and administrative purposes, though the older systems are still used casually and shown here for reference.

How each age is calculated

International age adds 1 year on each birthday and is what this tool highlights as the main result. Year age is simply the reference year minus the birth year, changing on January 1st regardless of birth month. Counting age is year age plus 1, since traditionally a newborn was already considered 1 year old at birth.

Frequently asked questions

Which age is now legally used in Korea?

Since the "Man Age Unification Act" took effect in June 2023, international age (man-nai) is the standard for essentially all legal, medical, and administrative contexts in South Korea. Counting age and year age are largely informal now.

Why is counting age always 1 or 2 years higher than international age?

Counting age treats a newborn as already 1 year old and adds a year on New Year's Day rather than on the birthday, so depending on how close your birthday is to the start of the year, counting age runs 1 or 2 years ahead of international age for most of the year.

Are there exceptions where Korea still uses year age?

Year age is still commonly used informally for things like age-based school grade cutoffs, the legal drinking/smoking age, and military conscription eligibility, even though international age is the general legal default.