Korean age vs international age explained
Since June 28, 2023, Korean law and administration use international age. Everyday life still mixes three systems, so here is how each one works and how to calculate it.
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Three ways to count age
- International age (man-nai): you are 0 at birth and gain a year on each birthday. Since June 28, 2023 it is the default age in Korean law, contracts and administration.
- Year age (yeon-nai): the current year minus your birth year. Everyone gains a year on January 1, regardless of birthday.
- Counting age (“Korean age”): you are 1 at birth and gain a year every January 1. This is the traditional system long used in everyday Korean life.
How to calculate
International age is the current year minus your birth year, minus one more if this year’s birthday hasn’t arrived yet. Year age is the current year minus the birth year, and counting age is year age plus one.
Example: born May 10, 2000, on March 1, 2026
| System | Calculation | Age |
|---|---|---|
| International age | 2026 − 2000 = 26, minus 1 before the birthday | 25 |
| Year age | 2026 − 2000 | 26 |
| Counting age | Year age + 1 | 27 |
The same person on the same day can be up to two years apart depending on the system. After the birthday (say, June 1) the international age becomes 26.
Where year age is still used
Some laws keep their own rule even after the switch. Notably, the age for buying alcohol and tobacco under the Juvenile Protection Act and the age for military service duties are judged by year age. School entry is also decided by birth year, not birthday.
Common mix-ups
- For age-restricted contracts, insurance or loans, check whether international age applies.
- Foreign documents and passports always use international age.
- Enter a birth date in the AlphaKit age calculator to see international, year and counting age plus the days until your next birthday, and change the reference date to check the age on any day.