Korean Counter Il (일): How to Count Days in Korean

What you'll learn

• Count days from one to ten with both 일 and the native day words.
• Choose between 삼 일 and 사흘 by length and setting.
• Ask 며칠 걸려요? ("how many days does it take?") and answer.
• Read and say a trip length such as 삼 박 사 일.
• Tell a counted span of days (3일) from a calendar date (3일).
• Prerequisites: Sino-Korean numbers 1-10. Estimated time: 20 minutes.

Korean Counter Il: the Essentials

The Korean counter il (일) is the Sino-Korean word for "day" used as a counter, and it follows a Sino-Korean number: 이 일 (two days), 삼 일 (three days), 십 일 (ten days). It measures a duration, which is a length of time, not a point in time. A parallel set of native day words also exists, and they are more common in everyday speech for the first few days.

In writing, the Sino pattern is regular: number plus 일. Linking changes the sound when a final consonant meets the vowel of 일, so 육 일 sounds like [유길], 칠 일 like [치릴], 팔 일 like [파릴] and 십 일 like [시빌]. The spelling stays the same, and the pronunciation follows the 국립국어원 standard pronunciation rules on liaison (연음).

The native day words are nouns in themselves. 하루 already means "one day", so you do not add a counter or the word 일 after it: 이틀 걸려요 ("It takes two days"), not 이틀 일 걸려요. The next step is placing both sets in a sentence.

How Do You Use 일 in a Sentence?

To use 일 in a sentence, put the Sino number and 일 first, then add a time word such as 동안 (for), 전 (ago), 후 (later) or 간 (a span of). The native day words follow the same patterns and take the same time words.

• 삼 일 동안 여행했어요. "I travelled for three days."
• 오 일 전에 도착했어요. "I arrived five days ago."
• 이틀 후에 다시 올게요. "I will come again in two days."
• 하루에 세 번 약을 먹어요. "I take the medicine three times a day."

The suffix 간 means "a span of", and it attaches straight to the counter: 삼 일간 is "for three days" without 동안. Both work, but 동안 is the safer choice when speaking.

Two tiny patterns are very useful. 매일 means "every day" and 날마다 means the same in a slightly softer way. 하루걸러 means "every other day", from 걸러 ("skipping"), and 이틀에 한 번 says the same thing as "once every two days". These repeated-habit phrases come up as soon as you talk about gym visits or medicine.

All of these patterns depend on a rule about which numbers go with 일, and that rule has a twist.

Which Number System Does 일 Take?

일 takes Sino-Korean numbers without exception, and the native day words replace the counter entirely. The Sino-Korean series is the same one used for dates, money and floors. The native series works differently: you do not count 한 일, 두 일; you use the fixed words 하루, 이틀, 사흘.

This matches the split explained in Sino vs native Korean numbers. Spoken Korean follows a tendency that is worth knowing:

• 1 to 4 days: the native words 하루, 이틀, 사흘, 나흘 are the default in speech.
• 5 to 10 days: both appear. 닷새 and 열흘 are common, while 엿새, 이레, 여드레 and 아흐레 sound old-fashioned and are used mostly in writing or set phrases.
• Beyond 10 days: Sino numbers dominate: 십오 일, 이십 일, 삼십 일.

For 15 days there is also a special word, 보름, which comes from the half-month of the moon and is still used in everyday speech. Beyond 열흘 the native words continue (열하루 for eleven days, 열이틀 for twelve), but speakers stop using them and say 십일 일, 십이 일 instead.

Expert insight: if you hesitate, use the Sino form with 일. 삼 일 is never wrong in any setting, and it grows to any size. Use the native words for the first four days, because that is what Korean speakers usually do.

What Does 일 Not Count?

일 counts only days. The same sound, 일, appears in other meanings, and Korean has separate words for neighbouring periods.

The first two rows are written identically with digits. A date (the 3rd) and a duration (three days) both read 삼 일, and only the surrounding words separate them. Look at the particle or time word:

• 3일에 만나요. "Let's meet on the 3rd." The particle 에 points to a calendar day.
• 3일 동안 만났어요. "We met for three days." The time word 동안 points to a span.

This is the reason the native word 사흘 is useful: in modern speech it almost always means a duration, not a date. If you want to be sure the listener hears "three days" and not "the 3rd", say 사흘. The names of the days of the month are listed in days of the month, and other periods have their own lessons: the 주 counter, the 달 and 개월 counters and the 년 counter. The same stem 일 also means "work", as in 일이 많아요 ("I have a lot of work"), so 삼 일 일했어요 can mean "I worked for three days".

Counting days is half the picture; the other half is asking the question.

How Do You Ask How Many Days?

Ask 며칠 걸려요? to ask how many days something takes. 며칠 is a fixed question word that means both "how many days?" and "what date?". It replaces 몇 일, which is a common but incorrect spelling.

Notice that 며칠 걸려요 asks about time needed, while 오늘 며칠이에요 asks the date. In the first, the answer is a duration (사흘); in the second, the answer is a date (구 일 meaning "the 9th"). The pronunciation of 며칠 is [며칠], and there is no extra consonant.

To say "about" or "a few", combine two numbers or use a fixed word:

In a statement, 며칠 means "a few days": 며칠 쉬었어요 is "I rested for a few days". The shift from question to statement comes from context and tone.

Trips: Nights and Days

Korean counts a trip in nights first and days second. 삼 박 사 일 (sam bak sa il) means three nights and four days. The word 박 (泊) counts nights spent away from home, and it takes Sino-Korean numbers, just like 일. The day count is almost always one higher than the night count.

The two counters are read as a pair and written as digits in schedules: 3박 4일. At a hotel desk or travel agency, the question is 며칠 묵으세요? ("How many days will you stay?"), where 묵다 means "to stay overnight". The answer is usually a nights-and-days pair.

A hotel exchange shows how the two systems sit together:

The clerk restates the stay with the native word 사흘 (사흘 밤, three nights), and the guest uses the Sino pair. The floor is written 2층 (read 이 층) so it cannot be misread as 이 층, "this floor". Both are correct, and switching like this is normal. The next dialogue is a shop delivery.

Two Short Conversations

An online order. The customer asks about delivery, and the shop answers with an approximate range.

Every number here is a day phrase: 며칠 (question), 이삼 일 (approximate Sino pair), 하루 (one native day). The word 더 means "more", so 하루 더 is "one more day".

A holiday plan. Two friends talk about leave from work.

The first answer uses a Sino number (오 일) for the total, then the native words 사흘 and 이틀 for the two parts. The total uses Sino because the native word for five days, 닷새, sounds old-fashioned to many speakers, while the parts use native words because 사흘 and 이틀 are the everyday choice for short stretches.

Worked Example: a Week in Korea

A learner describes a trip in four sentences.

1. 한국에 육 박 칠 일 동안 있었어요. "I stayed in Korea for six nights and seven days." A Sino nights-and-days pair, followed by 동안.
2. 서울에서 사흘, 부산에서 나흘 보냈어요. "I spent three days in Seoul and four days in Busan." Native day words for the two parts of the stay.
3. 기차로 세 시간 걸렸어요. "It took three hours by train." Hours use 시간 with native 세, a different counter.
4. 며칠 더 있고 싶었어요. "I wanted to stay a few more days." 며칠 as "a few days".

The checkpoint: the pair 육 박 칠 일 is Sino throughout, the parts 사흘 and 나흘 are native, and 며칠 is the only word that can be a question or a statement. If any of these feels uncertain, the next section lists the common slips.

Common Mistakes and Fixes

• 세 일 → 삼 일 or 사흘. The counter 일 takes Sino numbers.
• 몇일 → 며칠. 며칠 is a fixed word, always spelled this way.
• 하루 일 → 하루. 하루 already means "one day".
• 일 일 for one day → 하루. 일 일 is rare and looks like the date "the 1st".
• 삼 박 삼 일 for a three-night trip → 삼 박 사 일. A trip's day count is one higher than its night count.
• 3일 read as "the 3rd" when you mean a span → 사흘. Native day words remove the doubt.

Learners often assume that 일 can be added to any number, native or Sino. Actually the native words stand alone as nouns (사흘 is "three days" by itself), and only Sino numbers need 일 after them. The practice set below tests each of the six points.

Practice Set

Say each answer aloud, then check below.

1. "two days" (native word)
2. "ten days" (Sino)
3. "How many days does it take?"
4. "three nights, four days"
5. Fix the error: 세 일 동안
6. Fix the error: 몇일 걸려요?
7. "for five days" (choose either form)

Answers: 1. 이틀. 2. 십 일. 3. 며칠 걸려요? 4. 삼 박 사 일. 5. 삼 일 동안 or 사흘 동안. 6. 며칠 걸려요? 7. 오 일 동안 or 닷새 동안.

If item 5 or 6 tripped you, return to the number-system table; if item 4 did, reread the trip section.

What This Lesson Does Not Cover

This lesson covers counting durations of days. It does not teach calendar dates in full (the 1st to the 31st, with irregular forms such as 초하루), the days of the week, or hours and minutes; each has its own lesson. The advice on native versus Sino day words describes tendencies in standard Seoul Korean, and individual speakers vary in how many native words they use past the fourth day.

What to Learn Next

Continue with calendar dates in days of the month, then count weeks with the 주 counter. Words such as 오늘, 어제 and 내일 are in Korean time expressions. The Time Counters section lists every period counter in order, and how Korean counters work explains the shared rules. With the Korean counter il in place, durations from one day to a month are within reach.

Frequently Asked Questions

Is it 3일 or 사흘? Both mean three days. 삼 일 is the Sino-Korean form and sounds written or formal. 사흘 is the native day word and is more natural in everyday speech for short spans of one to four days. Beyond about ten days, speakers switch to Sino-Korean forms such as 십오 일 and 이십 일.

What is 며칠? 며칠 is a fixed question word with two jobs. It asks how many days, as in 며칠 걸려요? ("How many days does it take?"), and it asks the date, as in 오늘 며칠이에요? ("What is today's date?"). It is always spelled 며칠. The spelling 몇일 is a common mistake.

How do I say "one day" in Korean? Say 하루. It is a native noun that means one day, a whole day or a single day, as in 하루 쉬었어요 ("I rested for a day"). The Sino-Korean 일 일 is rare because it looks like the date "the 1st". For two days, say 이틀, and for three, 사흘.

What is 박 in 삼 박 사 일? 박 (泊) counts nights spent away from home, and it takes Sino-Korean numbers. 삼 박 사 일 means three nights and four days, and 일 박 이 일 is one night and two days. Trip lengths always state nights first and days second, and the day count is one higher than the night count.

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