Korean age: 세는나이, 연 나이 and 만 나이
South Korea has counted age three different ways at the same time, in different places, for most of a century. Since 28 June 2023 one of the three is the legal default — but the other two did not disappear, and one of them still decides when you are conscripted.
The three counts
| System | How it is counted | Where it applies |
|---|---|---|
| 세는나이 (se-neun nai) — Korean age | One at birth; everyone gains a year together on 1 January. | Everyday speech, and the count most people mean when speaking Korean socially. |
| 연 나이 (yeon nai) — year age | Current calendar year minus year of birth. Zero in the year of birth. | Military service (병역법) and the Youth Protection Act (청소년 보호법), which governs alcohol and tobacco sales; school-year cohorts follow the same birth-year logic. |
| 만 나이 (man nai) — international age | Years completed since birth; increments on the birthday. | All civil, judicial and administrative documents since 28 June 2023, unless a specific law says otherwise. |
The gap between the highest and lowest is one or two years, and which it is depends only on whether the birthday has passed. Someone whose birthday is still ahead of them this year is two years older in 세는나이 than in 만 나이; on the day of their birthday the gap narrows to one.
What changed on 28 June 2023
In December 2022 the National Assembly amended the Civil Act (민법) and 행정기본법, the framework statute for administrative law, so that an age stated in a law, a contract or a public document means 만 나이 unless that law explicitly says otherwise. The amendments took effect on 28 June 2023. The change is widely called the 만 나이 통일법 — the "age unification law" — which is a nickname for the pair of amendments rather than the title of a statute.
It is a change to interpretation, not to speech. 세는나이 remains ordinary conversational Korean, and 연 나이 remains written into specific statutes that were deliberately left alone: conscription and the age limits on alcohol and tobacco are still keyed to birth year, because keying them to a birthday would mean people in the same school cohort crossing the line on different days.
What this page is and is not
The three figures below are arithmetic on calendar dates in the Asia/Seoul zone, computed at build time by the same module the calculator uses. That arithmetic is exact and tested.
The description of which statute uses which count is a summary for a reader, not legal advice, and statutes change. The authoritative text is at theNational Law Information Center (법제처).
Prose last reviewed 2026-08-19.
Worked examples
Ages as they stand on 20 August 2026 in Seoul, for four birthdates. These are baked into the page when the site is built, so they are current as of that date and do not need JavaScript to appear.
| Birthdate | 세는나이 | 연 나이 | 만 나이 | Birthday this year |
|---|---|---|---|---|
| Born 1 January 1990 — born on New Year’s Day | 37 | 36 | 36 | already passed |
| Born 31 December 1990 — born on the last day of the same year | 37 | 36 | 35 | still to come |
| Born 15 June 2000 — a mid-year birthday | 27 | 26 | 26 | already passed |
| Born 25 December 2003 — a birthday still to come this year | 24 | 23 | 22 | still to come |
The New Year jump
The sharpest illustration is a newborn either side of midnight on 1 January. Both are days old; in 세는나이 they are a year apart.
| Birthdate | 세는나이 on 1 January 2026 | 연 나이 | 만 나이 |
|---|---|---|---|
| Born 31 December 2025 (Seoul) | 2 | 1 | 0 |
| Born 1 January 2026 (Seoul) | 1 | 0 | 0 |
A baby born on 31 December is two by 세는나이 when it is two days old. This is the fact most often quoted about Korean age, and it is the reason the 2023 amendments were framed as removing confusion rather than changing anyone's age.
A note on the new year that is used
Modern 세는나이 increments on 1 January, the solar new year. This distinguishes it from the Chinese 虚岁 and Vietnamese tuổi mụ, which are the same idea counted against Lunar New Year — so those two turn over on a date that moves between late January and late February. TheLunar New Year reference table lists that date for every year from 1901 to 2099.
Which one should you use
For anything official in South Korea, 만 나이 — that is what the 2023 amendments settled. For conscription, school year and age-restricted purchases, 연 나이. For answering the question a Korean speaker is actually asking when they ask your age in conversation, 세는나이 is still the one they mean, and saying it does not make you wrong about the law.