What is 階 (かい)?
階 (kai) is the counter for floors or stories of buildings. It has minimal sound changes compared to other counters.
3階に住んでいます
"I live on the 3rd floor"
エレベーターで5階まで
"To the 5th floor by elevator"
Complete 階 Counter Chart
| Number | Reading | Romaji | Note |
|---|---|---|---|
| 1 階 | いっかい | ikkai | ground floor |
| 2 階 | にかい | ni-kai | |
| 3 階 | さんがい | san-gai | sound change! |
| 4 階 | よんかい | yon-kai | |
| 5 階 | ごかい | go-kai | |
| 6 階 | ろっかい | rokkai | |
| 7 階 | ななかい | nana-kai | |
| 8 階 | はちかい/はっかい | hachi-kai | |
| 9 階 | きゅうかい | kyuu-kai | |
| 10 階 | じゅっかい/じっかい | jukkai |
Larger Numbers
11階 = じゅういっかい
20階 = にじゅっかい
30階 = さんじゅっかい
50階 = ごじゅっかい
100階 = ひゃっかい
Sound Change Note
The main sound change is:
- 3 階 = さんがい (not さんかい)
Most other numbers keep かい, though some have variations:
- 6 階 = ろっかい (っ inserted)
- 8 階 = はちかい or はっかい
- 10 階 = じゅっかい or じっかい
Basement Floors
地下 (ちか) = Underground/Basement
地下1階 (ちかいっかい) - B1
地下2階 (ちかにかい) - B2
地下3階 (ちかさんがい) - B3
Shortened forms:
B1 = ビーワン
B2 = ビーツー
地下 = ちか (basement in general)
駐車場は地下2階です
"The parking lot is on B2"
地下に行ってください
"Please go to the basement"
Asking "Which Floor?"
何階 (なんがい/なんかい)
Both readings are acceptable:
何階ですか？
"Which floor?"
何階に住んでいますか？
"Which floor do you live on?"
オフィスは何階ですか？
"Which floor is the office on?"
エレベーターは何階に止まりますか？
"Which floors does the elevator stop at?"
Common Patterns
〜階 + に (location particle)
3階に住んでいます
"I live on the 3rd floor"
5階にオフィスがあります
"The office is on the 5th floor"
2階に行ってください
"Please go to the 2nd floor"
〜階 + まで (up to)
エレベーターで10階まで
"To the 10th floor by elevator"
階段で3階まで歩きます
"I'll walk up to the 3rd floor by stairs"
〜階 + です (identification)
A: オフィスは何階ですか？
"Which floor is the office?"
B: 5階です
"It's on the 5th floor"
Building Terms
Floor-Related Vocabulary
1階 = ground floor/first floor
最上階 (さいじょうかい) = top floor
中階 (ちゅうかい) = middle floors
高層階 (こうそうかい) = high floors
低層階 (ていそうかい) = low floors
Building Types
〜階建て (〜かいだて) = story building
5階建て = 5-story building
10階建てのビル = 10-story building
20階建てのマンション = 20-story apartment
このビルは15階建てです
"This is a 15-story building"
30階建てのタワーマンション
"A 30-story tower apartment"
Common Conversations
Example 1: Elevator
A: 何階ですか？
"Which floor?"
B: 7階お願いします
"7th floor, please"
A: はい
"Sure"
Example 2: Apartment Viewing
A: こちらのマンションは何階建てですか？
"How many stories is this apartment building?"
B: 10階建てです
"It's 10 stories"
A: 今日見るのは何階ですか？
"Which floor are we viewing today?"
B: 8階です
"The 8th floor"
Example 3: Office Building
A: 田中さんのオフィスは何階ですか？
"Which floor is Mr. Tanaka's office?"
B: 15階です
"15th floor"
A: ありがとうございます
"Thank you"
Example 4: Department Store
A: おもちゃ売り場は何階ですか？
"Which floor is the toy department?"
B: 5階でございます
"It's on the 5th floor"
A: エレベーターはどこですか？
"Where's the elevator?"
B: あちらです
"Over there"
Special Expressions
〜階の (possessive)
3階の部屋
"A room on the 3rd floor"
5階のレストラン
"The restaurant on the 5th floor"
最上階の眺め
"The view from the top floor"
〜階まで (up to)
階段で5階まで
"Up to the 5th floor by stairs"
エレベーターで最上階まで
"To the top floor by elevator"
〜階ずつ (floor by floor)
一階ずつ上がります
"Go up floor by floor"
2階ずつ飛ばして
"Skip every other floor"
Floor Counting: US vs Japanese
Important cultural note:
American System
1st floor = ground level
2nd floor = one level up
British/Japanese System
Ground floor (1階) = ground level
1st floor (2階) = one level up
In modern Japanese buildings, 1 階 typically means ground floor (American 1st floor).
Department Store Floors
Common floor designations:
地下1階 = 食品売り場 (food)
1階 = 化粧品 (cosmetics)
2階 = 婦人服 (women's clothing)
3階 = 紳士服 (men's clothing)
4階 = 子供服 (children's clothing)
5階 = おもちゃ (toys)
6階 = レストラン街 (restaurants)
屋上 (おくじょう) = rooftop
Room Numbers
Combining floor and room:
301号室 (さんびゃくいちごうしつ)
"Room 301" (3rd floor, room 1)
502号室 (ごひゃくにごうしつ)
"Room 502" (5th floor, room 2)
1205号室 (せんにひゃくごごうしつ)
"Room 1205" (12th floor, room 5)
Common Mistakes
Mistake 1: Wrong reading for 3 階
Wrong: さんかい ❌
Right: さんがい ✓
"3rd floor"
Mistake 2: Confusing 何階 readings
Both are acceptable:
なんがい ✓
なんかい ✓
"Which floor?"
Mistake 3: Forgetting 地下 for basement
Wrong: マイナス1階 ❌
Right: 地下1階 ✓
"B1"
Mistake 4: Wrong 〜階建て usage
Wrong: 10階の建物 ⚠️ (unclear)
Right: 10階建ての建物 ✓
"10-story building"
Elevator Phrases
Common Elevator Expressions
何階ですか？
"Which floor?"
〜階お願いします
"〜th floor, please"
開 (あけ) - Open
閉 (しめ) - Close
エレベーターで参ります
"I'll take the elevator"
階段で行きます
"I'll take the stairs"
Elevator Announcements
1階です
"First floor"
ドアが閉まります
"The doors are closing"
上に参ります
"Going up"
下に参ります
"Going down"
Formal vs Casual
Casual
何階？
"Which floor?"
3階に住んでる
"I live on the 3rd floor"
5階まで
"To the 5th floor"
Polite
何階ですか？
"Which floor?"
3階に住んでいます
"I live on the 3rd floor"
5階までお願いします
"To the 5th floor, please"
Formal
何階でございますか？
"Which floor is it?" (very polite)
3階でございます
"It's on the 3rd floor"
エレベーターで5階までご案内いたします
"I'll guide you to the 5th floor by elevator"
Related Expressions
上の階 (うえのかい) - Upper floor
上の階がうるさい
"The floor above is noisy"
一つ上の階
"One floor up"
下の階 (したのかい) - Lower floor
下の階に降ります
"I'll go down to the floor below"
2つ下の階
"Two floors down"
同じ階 (おなじかい) - Same floor
同じ階に住んでいます
"We live on the same floor"
Practice Sentences
Basic
3階に住んでいます
"I live on the 3rd floor"
オフィスは5階です
"The office is on the 5th floor"
地下1階に駐車場があります
"There's a parking lot on B1"
Intermediate
このビルは何階建てですか？
"How many stories is this building?"
エレベーターで10階まで行ってください
"Please take the elevator to the 10th floor"
最上階からの眺めは素晴らしいです
"The view from the top floor is wonderful"
Advanced
私のオフィスは15階建てのビルの8階にあります
"My office is on the 8th floor of a 15-story building"
地下2階から屋上まで、全部で22階あります
"From B2 to the rooftop, there are 22 floors in total"
一階ずつエレベーターが止まるので、時間がかかります
"The elevator stops at every floor, so it takes time"
Related Grammar Points
- Counter System Basics - How counters work
- Number System Overview - Japanese numbers
- Location particles - に、で、まで
- Building vocabulary - Architecture terms
- Direction words - 上、下、同じ
- 〜号室 - Room numbers