Korean Age Explained: 세는 나이 vs 만 나이 (and the 2023 Law)

Ask a Korean speaker how old they are and you may get two different numbers, both correct. 세는 나이 counts a newborn as one and adds a year every January 1; 만 나이 counts from zero and adds a year on your birthday, exactly like the international system. Since the 만 나이 통일법 took effect on June 28, 2023, the second count is the legal standard — and both still turn up in conversation. Here is how each one is calculated, and the vocabulary for saying an age out loud.

Two counts, one person

세는 나이 has two rules. A baby is one year old at birth, and everybody gains a year together when the calendar year changes. Birthdays are celebrated, but they do not move this number. That is why a baby born in late December is one at birth and two a few days later, while a baby born in January stays one for almost twelve months.

만 나이 is the count used across most of the world. You start at zero and add a year on each birthday. For any given person the two numbers sit one or two apart, depending on whether their birthday has already passed this year.

The gap creates a familiar exchange: 만으로 몇 살이에요? — how old are you in the 만 count? The word 만 in front of the number is the shortcut for saying which system you mean, and it appears on forms as well as in speech.

What the 만 나이 통일법 did

The 만 나이 통일법 took effect on June 28, 2023. It made 만 나이 the standard reading of age in laws and administrative documents, so that a number written on an official form now means the international count unless something says otherwise. Everyday speech was not rewritten by a law, and both counts still circulate — which is why people frequently mark the count they are using rather than leaving it to guesswork.

There is a third calculation still visible in some rules, usually called 연 나이: the current year minus your birth year. It ignores the birthday entirely, which is what makes it convenient for anything organised by school year or cohort.

Saying an age out loud: 살 and 세

Two counters carry age, and they take different number sets. 살 goes with native Korean numbers — 한 살, 두 살, 열 살, 스무 살, 서른 살 — and this is what you hear in conversation. 세 goes with Sino-Korean numbers — 이십 세, 삼십오 세 — and lives on documents, in medical settings and in news writing.

Watch the number that goes with 살, because native numbers change shape in front of a counter: 하나 becomes 한, 둘 becomes 두, 스물 becomes 스무. So it is 스무 살, never 스물 살. Both number sets are laid out side by side in our Korean numbers guide, and the counter patterns get more practice in the native numbers and counters lesson.

Age also matters because it feeds the address system: once two people know who is older, the words they call each other are largely settled — which is the subject of our oppa, unnie, hyung and noona map. A quick answer for the moment someone asks: 동갑이에요 if you share a birth year, 제가 한 살 위예요 if you are a year older, and 만으로는 스물세 살이에요 if you want to be precise about which count you mean.