Age in Native Numbers: 살 and 몇 살

If you ever wondered why Korean bothers keeping a whole second set of numbers alive — the native 하나·둘·셋 and the tens 스물·서른·마흔 — age is the answer. In everyday conversation, Koreans state their age with a native number plus the counter 살: 스무 살, 서른 살, 마흔 살. This is the single most frequent place the native tens show up, which is why they're worth over-learning, and it's also where the system's one nasty little reduction — 스물 shrinking to 스무 — bites hardest. This page gives you the everyday age register; the respectful and formal registers (연세, 세) get their own companion page.

Native number + 살

The pattern is simply native number + 살. Past the teens, "native number" means one of the native tens, optionally with a unit attached.

Because 살 begins with a consonant and 이에요 begins with a vowel, the two run together in speech — 살이에요 liaises to [사리에요], which is what the romanization sarieyo reflects. The tens themselves (서른, 마흔, 쉰, 예순…) are ten separate memorized words with no derivable link to their ones-digits; if they still feel shaky, drill them on the native tens page.

The reduction that bites: 스물 → 스무

Here is the one irregularity you cannot skip. When 20 stands alone in front of 살, 스물 loses its final ㄹ and becomes 스무: it's 스무 살, never ×스물 살. This is the same shape-shift that 하나→한, 둘→두, 셋→세 undergo before any counter (see the forms that change before counters) — but 스물 is the one that catches learners, precisely because its neighbors don't do it. 서른, 마흔, 쉰 all keep their full shape.

Compounds: only the unit shifts, and 스물 comes back

Now the twist on the twist. The 스물→스무 reduction happens only when 20 stands alone before the counter. The moment you add a unit — 21, 25, 26 — the number is no longer bare 20, so 스물 keeps its full form, and it's the unit at the end that may shape-shift instead.

• 21 = 스물 + 하나 → 하나 shifts to 한 → 스물한 살 (스물 stays!)
• 25 = 스물 + 다섯 → 다섯 doesn't shift → 스물다섯 살 (스물 stays!)

So you get the striking contrast: 20 is 스무 살, but 21 is 스물한 살 and 25 is 스물다섯 살. There is no ×스무한 살.

Asking: 몇 살이에요? and 몇 살이세요?

The casual question is 몇 살이에요? — literally "how many 살?" (Here 몇 is the "how many" word; 살이에요 liaises to sarieyo, and the whole thing is really pronounced with a tensed 살 — [멷쌀] — though the romanization keeps the spaced words separate.)

Bumping the politeness up a notch, you add the honorific -시- to the copula: 몇 살이세요?. This is warmer and more respectful — appropriate for someone a little older or someone you've just met — while still being a normal, askable question among peers and near-peers.

A word on the 2023 age reform

If you've heard that "Korean ages changed," here's the accurate version. In June 2023 Korea officially adopted 만 나이 (international age — 0 at birth, +1 on each birthday) as the legal and administrative standard, replacing the traditional 세는나이 (Korean age — 1 at birth, +1 for everyone on New Year's Day). The upshot: many people's stated age dropped by one or two years overnight.

Crucially, none of this touches the grammar on this page. You still count in native numbers + 살 exactly as before — the reform changed which number you land on, not how you say it. 스무 살 is still 스무 살; it just now means the international twenty.

Common Mistakes

1. Failing to reduce 스물 for a bare 20. Twenty years old is 스무 살.

• ✗ 스물 살이에요.
• ✓ 스무 살이에요. — seumu sarieyo — "I'm twenty." (but 서른 살, 마흔 살 keep their shape)

2. Over-reducing in the compounds. 21 keeps 스물; there is no ×스무한 살.

• ✗ 스무한 살, ×스무다섯 살
• ✓ 스물한 살, 스물다섯 살 — seumulhan sal, seumuldaseot sal — "21, 25 years old"

3. Putting a Sino number on 살. Casual age wants a native number.

• ✗ 삼십 살이에요.
• ✓ 서른 살이에요. — seoreun sarieyo — "I'm thirty." (The formal register does use Sino — 삼십 세 — but with the counter 세, not 살.)

4. Asking a clear elder 몇 살이에요. Blunt to the point of rude. Use the honorific noun.

• ✗ 할머니, 몇 살이에요?
• ✓ 할머니, 연세가 어떻게 되세요? — halmeoni, yeonsega eotteoke doeseyo — "Grandmother, how old are you?"

5. Forgetting the liaison in speech. 살이에요 runs together as [사리에요] — don't insert a pause after 살.

• Written: 스무 살이에요
• Said: [스무 사리에요] — seumu sarieyo

Key Takeaways

• Everyday age is native number + 살: 다섯 살, 스무 살, 서른 살, 마흔 살. This is the flagship use of the native tens.
• 스물 → 스무 for a bare 20 (스무 살, never ×스물 살) — but 서른/마흔/쉰 don't reduce, and in compounds 스물 comes back: 스물한 살, 스물다섯 살.
• Ask casually with 몇 살이에요?, a touch more politely with 몇 살이세요? — but for a senior person, switch to 연세가 어떻게 되세요?.
• The 2023 만 나이 reform lowered stated ages by 1–2 years but left the 살 grammar untouched.