Japanese numbers, dates and time: reading them without freezing

Numbers are where confident learners suddenly stall. You know the words, but the cashier says 千八百六十円 at conversational speed and your brain refuses to convert it; you know 四 is yon until someone says 四月 and it turns into shi; you can count to a hundred but 100,000 comes out wrong because Japanese groups digits in fours, not threes. None of this is difficult — it is just a specific, finite set of irregularities that nobody lays out in one place. This guide lays them out, with the reference tables you will want to come back to.

1. Two counting systems, and when each one appears

Japanese has two parallel sets of numbers. The Sino-Japanese set (いち, に, さん…) was borrowed from Chinese and is used for essentially everything: arithmetic, prices, phone numbers, dates, times, and combination with counter words. The native Japanese set (ひとつ, ふたつ, みっつ…) is much older, stops dead at ten, and survives as a general-purpose counter for physical objects when you don't know or don't need the specific counter.

The native set is genuinely useful, not a museum piece. In a shop, りんごを三つください (りんごを みっつ ください) — "three apples, please" — is what an ordinary person says, and it works for apples, boxes, chairs, ideas, and anything else you have no counter for. Past ten it simply stops: eleven apples is りんご十一個 (じゅういっこ) with the counter 個, or りんごを十一 in a pinch. Notice also that 十 alone is じゅう but the native "ten" is とお, with a long vowel — those are different words that happen to share a kanji. Specific counters (本 for long things, 枚 for flat things, 匹 for small animals) are a whole topic of their own; the counters guide covers them, and the つ series is your safety net until you have them memorised.

2. The 4 / 7 / 9 problem

Three numbers have two Sino-Japanese readings each, and choosing wrongly is the most audible number mistake a learner makes. The general default is よん, なな, きゅう — use those when counting aloud, giving a quantity, or reading a figure, and you will be right most of the time. But a specific set of time and date words locks in the older readings し, しち, く instead, and those are fixed: there is no version of "April" pronounced よんがつ.

Look closely at the 4 row: 四月 is shi, 四時 is yo (not よん, not し), 四分 is yon, and 四人 is yo. That single digit takes three different shapes depending on what follows it. There is no rule to derive this from — it has to be learned as vocabulary, item by item, which is exactly what the tables in this guide are for. The good news is that the list is short and closed. Once 四時 (よじ), 四人 (よにん), 四日 (よっか) and 四月 (しがつ) are automatic, you have covered nearly all the traffic.

Zero has options too. 零 (れい) is the formal reading used in broadcasts and official contexts, ゼロ is the everyday borrowed form, and 〇 read as まる ("circle") turns up in phone numbers and room numbers. When reading a phone number aloud, Japanese speakers say the digits one at a time and lengthen some for clarity: 03-1234-5678 becomes ゼロ さん の いち にー さん よん の ごー ろく なな はち, with の standing in for the hyphens and に and 五 stretched to にー and ごー so they cannot be misheard.

3. Tens, hundreds, thousands — and the sound changes hiding in them

Building numbers is mechanical: 十 (じゅう) is ten, so twenty is 二十 (にじゅう), thirty-five is 三十五 (さんじゅうご), ninety-nine is 九十九 (きゅうじゅうきゅう). No exceptions in the tens at all. Hundreds and thousands are almost as regular, except that a handful of combinations trigger consonant changes that make them sound nothing like their parts:

• 百 (ひゃく) = 100. Say ひゃく on its own — never いちひゃく. The changes: 300 = 三百 さんびゃく, 600 = 六百 ろっぴゃく, 800 = 八百 はっぴゃく. All others are plain: 200 にひゃく, 400 よんひゃく, 500 ごひゃく, 700 ななひゃく, 900 きゅうひゃく.
• 千 (せん) = 1,000. Again bare せん on its own. The changes: 3,000 = 三千 さんぜん, 8,000 = 八千 はっせん. All others plain: 2,000 にせん, 4,000 よんせん, 5,000 ごせん, 6,000 ろくせん, 7,000 ななせん, 9,000 きゅうせん.
• 万 (まん) = 10,000. Here the pattern flips: you must say the いち. 10,000 is 一万 (いちまん), never bare まん. No consonant changes occur with 万 at all — 三万 さんまん, 八万 はちまん, all regular.

Put those together and a mid-sized number decomposes cleanly. 3,865 is 三千八百六十五 = さんぜん・はっぴゃく・ろくじゅう・ご, with two sound changes in the first half and none in the second. Say it in four chunks rather than as one word; that is how it is heard, too.

4. The 万 wall: why 100,000 breaks English speakers

This is the genuine conceptual difficulty, and it has nothing to do with vocabulary. English groups digits in threes — thousand, million, billion — which is why we write commas every three places. Japanese groups them in fours: 万 (10⁴), 億 (10⁸), 兆 (10¹²). The comma placement in written Japanese still follows the Western three-digit convention, so the digits on the page fight the reading in your head. That mismatch, not the words, is what makes you freeze.

The practical trick is to stop translating and start re-grouping the digits by fours from the right. Take 25,000,000. Slice from the right in fours: 2500|0000. The right block is the 万 block, the left block counts 万s, so this is 二千五百万 (にせんごひゃくまん) — "2,500 万". You never had to think about "twenty-five million" at all. Do this a dozen times with real figures — populations, salaries, house prices — and the four-digit slice becomes automatic. Two anchors worth memorising outright, because they come up constantly: 一億 is 100 million (Japan's population is about 一億二千万人, いちおく にせんまんにん), and 一万円 is the largest banknote.

5. Money: the numbers you'll hear most

Prices are where numbers stop being an exercise. The counter is 円 (えん) and it attaches with no sound changes of its own, so all the difficulty is in the number itself. Coins run 1, 5, 10, 50, 100 and 500 yen; notes are 1,000, 5,000 and 10,000 yen, plus a rarely-seen 2,000. Some worked prices, chunked the way they are spoken:

• 380円 → さんびゃく はちじゅう えん (note the 三百 change)
• 1,280円 → せん にひゃく はちじゅう えん
• 3,800円 → さんぜん はっぴゃく えん (two changes in a row)
• 6,600円 → ろくせん ろっぴゃく えん
• 12,500円 → いちまん にせん ごひゃく えん

The surrounding phrases matter as much as the figures. いくらですか (how much is it?) is the question; the answer usually arrives as 〜円です or, in service language, 〜円になります. At the till you will hear 千円からお預かりします (せんえんから おあずかりします, "taking 1,000 yen from you") and お釣りです (おつりです, "here's your change"). Price tags distinguish 税込 (ぜいこみ, tax included) from 税抜 (ぜいぬき, tax excluded) — always check which, since the shelf price and the till price can differ. And カードで払えますか (カードで はらえますか, "can I pay by card?") is worth having ready. These sit alongside the ordering vocabulary in the menu reading guide, which is the other half of surviving a Japanese shop.

6. Dates: months are easy, days of the month are not

Months are almost free. Take the Sino number, add 月 (がつ): 一月 いちがつ, 二月 にがつ, 三月 さんがつ, and so on through 十二月 じゅうにがつ. The only things to watch are the three from the 4/7/9 table — 四月 しがつ, 七月 しちがつ, 九月 くがつ — and the fact that 〜月 read がつ names a month, while 〜か月 read かげつ counts a duration of months: 三か月 (さんかげつ) is "three months long". The question word is 何月 (なんがつ).

Days of the month are the opposite: the first ten, plus 14th, 20th and 24th, use native readings that look nothing like the numbers in them. This table is the single densest thing to memorise in this whole guide, and it repays the effort every time you make an appointment.

Three notes on this table. First, the 14th and 24th inherit よっか, which is why they are irregular while the 4th's neighbours are not. Second, 17th / 19th / 27th / 29th keep the old しち and く readings even though they are otherwise regular. Third — and this is the trap that catches everyone — 四日 (よっか) and 八日 (ようか) differ in only their middle mora and are constantly confused in both directions. Say them next to each other, out loud, until the difference is physical: よっ-か has a glottal stop, よー-か has a long vowel. Getting this wrong moves a meeting by four days.

One more distinction: 一日 is ついたち when it means "the 1st of the month" but いちにち when it means "one day" as a length of time. 一日中 (いちにちじゅう) is "all day long". Every other date word doubles as its duration without changing — 三日 (みっか) is both "the 3rd" and "three days". Japanese writes full dates largest-unit-first, so 2026年8月9日 (にせんにじゅうろくねん はちがつ ここのか) is year, then month, then day. Official forms may also use the imperial era: 令和 (れいわ) began in 2019, so 2026 is 令和8年.

7. Days of the week and relative time

The weekday names are built from the same seven celestial elements behind the Romance-language weekdays, so they map across neatly and are unusually easy to remember. Each ends in 曜日 (ようび):

Ask with 何曜日ですか (なんようびですか). In casual speech and on timetables the 日 often drops: 月曜 (げつよう) is fine. 平日 (へいじつ) means weekdays, 週末 (しゅうまつ) the weekend, and 祝日 (しゅくじつ) a public holiday — worth knowing before you plan a trip, since Japan has a lot of them.

Relative time words follow a tidy grid with two deliberate holes in it:

The week and month rows are perfectly regular — 先 for past, 今 for present, 来 for future, doubled with 々 or 再 for one step further. The day and year rows break the pattern, and those are the ones to drill: 今年 is ことし, not ×こんねん, and "last year" is 去年 (きょねん), not ×先年. On the day row, 明日 has three readings of increasing formality — あした in speech, あす in announcements and news, みょうにち in very formal writing — and 一昨日 (おととい) and 明後日 (あさって) are single words rather than compounds you can derive. Two more irregulars worth adding: 今朝 (けさ) for "this morning" and 今晩 (こんばん) for "this evening". These are all early-stage vocabulary and appear in the N5 list.

8. Telling the time: 時 and 分

Hours use 時 (じ), and the only surprises are the three from the 4/7/9 table: 四時 よじ, 七時 しちじ, 九時 くじ. Everything else is the plain Sino number plus じ — 一時 いちじ, 二時 にじ, 三時 さんじ, 五時 ごじ, 六時 ろくじ, 八時 はちじ, 十時 じゅうじ, 十一時 じゅういちじ, 十二時 じゅうにじ. Add 午前 (ごぜん, a.m.) and 午後 (ごご, p.m.) before the time: 午後三時 is 3pm. 正午 (しょうご) is noon exactly.

Minutes use 分, and here the reading alternates between ふん and ぷん depending on the preceding sound. The pattern: numbers ending in 1, 3, 4, 6, 8 and 10 take ぷん; those ending in 2, 5, 7 and 9 take ふん. Several also change the number itself.

半 (はん) replaces 三十分 in ordinary speech: 七時半 (しちじはん) is half past seven, and it is far more common than 七時三十分. To express "before" and "past", use 前 (まえ) and 過ぎ (すぎ): 五分前 (ごふんまえ) is "five minutes to", 十時五分過ぎ is "just past ten". A caution that catches many learners: 十分 is じゅっぷん when it means "ten minutes", but the very same two characters read じゅうぶん mean "enough, sufficient" — 十分です can be "it's ten minutes" or "that's plenty", and only context separates them.

Keep points in time and lengths of time apart. 時 marks a clock position; 時間 (じかん) marks a duration. 二時 (にじ) is two o'clock, 二時間 (にじかん) is two hours. Note 四時間 is よじかん, keeping the よ. Timetables, tickets and official notices use the 24-hour clock — 18時30分発 (じゅうはちじ さんじゅっぷん はつ, "departing 18:30"). And a genuine quirk worth recognising: TV listings and nightlife flyers extend past midnight rather than resetting, so a programme at 1am may be printed as 25時 and a club night ending at 5am as 29時.

9. Question words, common mistakes, and how to drill this

Most number questions are formed with 何 plus the relevant counter, which makes them easy to generate once you know the counter: 何時 (なんじ, what time), 何分 (なんぷん, what minute / how many minutes), 何時間 (なんじかん, how many hours), 何日 (なんにち, what date / how many days), 何曜日 (なんようび, what day of the week), 何月 (なんがつ, what month), 何年 (なんねん, what year), 何人 (なんにん, how many people). Outside that pattern sit いくら (how much money) and いくつ (how many things, or how old). For age the counter is 歳 (さい) with its own irregulars — 一歳 いっさい, 八歳 はっさい, 十歳 じゅっさい, and 二十歳 read はたち rather than にじゅっさい. Asking someone's age politely, you say おいくつですか.

The mistakes that recur most often, in rough order of frequency:

1. Confusing 四日 (よっか) and 八日 (ようか). Drill them as a pair, never separately.
2. Saying ×よんじ or ×きゅうじ for 4 and 9 o'clock. They are よじ and くじ.
3. Saying ×よんがつ for April. It is しがつ, always.
4. Reaching for thousands where Japanese uses 万: 100,000 is 十万, not any arrangement of 千.
5. Adding いち to 百 and 千 (×いちひゃく) while dropping it from 万 (×まんえん). It is the reverse: ひゃく, せん, but いちまん.
6. Using the ひとつ series past ten, or with a counter attached (×三つ枚).
7. Mixing 時 and 時間: ×三時勉強しました means "I studied at three", not "I studied for three hours" (三時間勉強しました).

For practice, numbers reward a different method from ordinary vocabulary, because the target is speed rather than recall. Three drills that work. Read your own clock aloud in Japanese every time you check the time — you will hit every hour and a lot of the 分 table within a week. Read prices off receipts and shelf tags before you look at the total; a convenience store visit is thirty repetitions of the 百 and 千 sound changes. And say tomorrow's date and weekday out loud each night, which forces the irregular day-of-month readings into the same slot every day. Alongside that, run the underlying words as flashcards through the study page and keep the weak ones cycling in review; anything ambiguous is worth a second quiz pass rather than a guess. If the readings themselves are still shaky, that is a kana problem rather than a number problem — the kana module and the pronunciation guide come first, particularly for the doubled consonants in はっぴゃく and ろっぷん.