Korean's Two Number Systems: When to Use 하나, 둘 vs 일, 이

One of the biggest surprises for Korean learners is that Korean has two complete sets of numbers. Native Korean numbers developed within the language, while Sino-Korean numbers came from Chinese. Both are used every day, and choosing the wrong one can make a sentence sound strange. The good news is that each system has clear jobs.

Native Korean numbers

• 하나 (one), 둘 (two), 셋 (three), 넷 (four), 다섯 (five)
• 여섯 (six), 일곱 (seven), 여덟 (eight), 아홉 (nine), 열 (ten)
• 스물 (twenty), 서른 (thirty), 마흔 (forty), 쉰 (fifty)

Tens and ones combine simply: 열하나 is eleven, 스물다섯 is twenty-five. Native numbers are usually used only up to 99; above that, people switch to Sino-Korean.

• 하나, 둘, 셋!

  [hana dul set]

  One, two, three! (counting before a photo)

Sino-Korean numbers

• 일 (one), 이 (two), 삼 (three), 사 (four), 오 (five)
• 육 (six), 칠 (seven), 팔 (eight), 구 (nine), 십 (ten)
• 백 (hundred), 천 (thousand), 만 (ten thousand)

Sino-Korean numbers build logically: 십일 is eleven, 이십 is twenty, 이십오 is twenty-five, 백 is one hundred. The unit 만 (ten thousand) is important because Korean groups large numbers by four digits, not three. One hundred thousand is 십만, "ten ten-thousands."

When to use native numbers

• Counting things with counters: 사과 세 개 (three apples)
• Counting people: 두 명 (two people)
• Hours on the clock: 세 시 (three o'clock)
• Age in everyday speech: 스물다섯 살 (twenty-five years old)
• Counting times or occurrences: 한 번 (once)

• 사과 세 개 주세요.

  [sagwa se gae juseyo]

  Three apples, please.

• 저는 스물다섯 살이에요.

  [jeoneun seumuldaseot sarieyo]

  I'm twenty-five years old.

• 한 번 더 해 주세요.

  [han beon deo hae juseyo]

  Please do it one more time.

When to use Sino-Korean numbers

• Money: 오천 원 (five thousand won)
• Minutes and seconds: 삼십 분 (thirty minutes)
• Dates: 삼월 이십일 (March twentieth)
• Phone numbers, floors, room and bus numbers
• Measurements: 오 킬로 (five kilograms)

• 이거 오천 원이에요.

  [igeo ocheon wonieyo]

  This is five thousand won.

• 지금 두 시 삼십 분이에요.

  [jigeum du si samsip bunieyo]

  It's two thirty now.

• 삼 층에 있어요.

  [sam cheunge isseoyo]

  It's on the third floor.

Notice the time example: the hour uses native Korean (두 시), but the minutes use Sino-Korean (삼십 분). This mix is exactly why learners find numbers tricky at first.

Shortened forms before counters

Some native numbers change shape before a counter: 하나 becomes 한, 둘 becomes 두, 셋 becomes 세, 넷 becomes 네, and 스물 becomes 스무.

• 커피 두 잔 주세요.

  [keopi du jan juseyo]

  Two coffees, please.

• 고양이 한 마리가 있어요.

  [goyangi han mariga isseoyo]

  There is one cat.

• 스무 살이에요.

  [seumu sarieyo]

  I'm twenty years old.

Phone numbers

Phone numbers are read digit by digit with Sino-Korean numbers, and zero is usually 공.

• 공일공

  [gongilgong]

  zero-one-zero (the start of many mobile numbers)

Practice ideas

• Count objects around you with native numbers and a counter.
• Read prices aloud at stores with Sino-Korean numbers.
• Say the current time out loud a few times a day: native hour, Sino-Korean minutes.

Two number systems can feel like double the work, but each has a predictable role. Once you link each system to its situations, numbers become just another part of everyday Korean.