Numbers are usually the first thing a language course throws at you, and in Japanese they’re also one of the first things that quietly trips learners up. Not because the numbers are hard — the system from 1 to 100 is beautifully logical, arguably more logical than English — but because Japanese has two sets of numbers, several numbers have two accepted readings, and the moment you attach a number to an actual object, the pronunciation can shift under your feet.

The good news: once you understand the underlying pattern, you can build every number from 1 to 100 from about twelve building blocks. Let’s put those blocks in place.

Why Japanese Has Two Counting Systems

Japanese borrowed heavily from Chinese around the 5th–8th centuries, including a full set of numerals. Rather than replacing the native Japanese numbers, the borrowed ones sat alongside them, and the two systems divided up the labour.

• Sino-Japanese numbers (ichi, ni, san…) are the workhorses. Use them for maths, money, phone numbers, dates, times, addresses, and with almost every counter word. These go all the way up — and beyond.
• Native Japanese numbers (hitotsu, futatsu, mittsu…) only run from 1 to 10. They’re used for counting general objects when you don’t know or don’t need a specific counter, and for a handful of fixed expressions.

If you’re short on time, learn the Sino-Japanese set first. It covers roughly 90% of real situations. The native set is small enough to pick up afterwards in an afternoon.

Japanese Numbers 1–10 (Both Systems)

Notice that the native numbers 1–9 all end in -tsu, and that ten breaks the pattern with a simple tō. Notice too that several native forms are just the Sino root with a vowel change: futa- mirrors ni, mu- mirrors roku, ya- mirrors hachi. That doubling pattern (2→4, 3→6, 4→8) is a genuine historical feature, and it makes the set easier to memorise than it looks.

The Lego Rule: Building 11 to 99

Here’s where Japanese rewards you. There are no irregular teen words like “eleven”, “twelve” or “thirteen”. Every number from 11 to 99 is built by simple arithmetic spoken aloud.

• 11–19: say jū (10) + the digit. 11 = jū-ichi, 15 = jū-go, 19 = jū-kyū.
• Multiples of ten: say the digit + jū. 20 = ni-jū (literally “two tens”), 70 = nana-jū.
• Everything else: combine both. 47 = yon-jū-nana (“four tens seven”). 88 = hachi-jū-hachi.

Two things to lock in. First, 100 is hyaku, never ichi-hyaku — you don’t say the “one”, just as English doesn’t say “one hundred and…” in every context. Second, at the multiples of ten you should default to yon (40), nana (70) and kyū (90). Saying shi-jū or ku-jū will mark you instantly as a beginner.

Yon or Shi? Nana or Shichi? Kyū or Ku?

These three numbers are the single biggest source of learner anxiety, so here is the practical rule: default to yon, nana and kyū. They’re clearer, safer, and correct in the overwhelming majority of situations, especially in isolation, in phone numbers and with counters.

The alternatives survive in fixed expressions you’ll simply memorise as vocabulary:

• 四時 = yo-ji (4 o’clock) — not yon-ji or shi-ji.
• 七時 = shichi-ji (7 o’clock) is the standard reading.
• 九時 = ku-ji (9 o’clock) — not kyū-ji.
• 四月 = shi-gatsu (April), 七月 = shichi-gatsu (July), 九月 = ku-gatsu (September).

There’s a cultural reason shi and ku get avoided: shi sounds identical to 死 (“death”) and ku to 苦 (“suffering”). Many Japanese hospitals and hotels skip room and floor numbers containing 4 and 9, and gift sets are rarely sold in fours — a genuinely useful thing to know before you buy someone four of anything.

Zero, and Reading Numbers Aloud

Zero has three forms. Zero (ゼロ) is the everyday borrowing from English. Rei (零) is formal and appears in weather forecasts and written reports. Maru (まる, “circle”) is what people actually say when reading out phone numbers and codes digit by digit.

Phone numbers are read one digit at a time, always with yon, nana and kyū, with the hyphen spoken as no: 090-4783-2561 becomes zero-kyū-zero no yon-nana-hachi-san no ni-go-roku-ichi.

Counters: The Part Nobody Warns You About

In Japanese you can’t just say “three cats” — you need a counter word that classifies the noun, much like English “three sheets of paper” or “two loaves of bread”, except Japanese does it for everything. Worse, the number and counter fuse together and change sound.

The pattern behind the chaos is worth naming: numbers ending in a vowel-less sound (1 ichi, 6 roku, 8 hachi, 10 jū) tend to produce a doubled consonant before h-, k-, s- and t- counters, and an h- counter often softens to b- or p-. That’s why ichi + hon becomes ippon and san + hon becomes sanbon. You don’t need to derive it in real time — but recognising the logic means you’ll stop treating each counter as a random list.

A Sample Situation

You’re at a café. “Two coffees, please” = Kōhī o futatsu kudasai (コーヒーを二つください). Ordering four beers? Bīru o yon-hai kudasai — hai being the counter for cupfuls and glassfuls. Buying three stamps? Kitte o san-mai kudasai. Notice how the number and counter come after the object, not before it.

How to Actually Drill This

Reading a table is not learning. Three techniques that work faster than flashcards alone:

1. Count your day. Stairs, reps at the gym, items in your shopping basket — count them in Japanese out loud. Repetition in context beats repetition in isolation.
2. Read prices and clocks. Every time you see a receipt or a digital clock, convert it. This forces you into the yo-ji / ku-ji irregularities daily.
3. Learn counters in phrases, not lists. Memorise “bīru o nihon” as a chunk you’d actually say, rather than conjugating 本 through all ten numbers.

Frequently Asked Questions

Do I need to learn both Japanese counting systems?

Eventually, yes, but not simultaneously. Start with the Sino-Japanese set (ichi, ni, san…) because it scales infinitely and pairs with almost every counter. Add the native set (hitotsu, futatsu…) once the first is automatic — it’s only ten words, and it’s what you’ll use when ordering food or counting unfamiliar objects.

Why is 4 sometimes “yon” and sometimes “shi”?

Shi is the original Chinese-derived reading, but it’s a homophone of 死 (“death”), so speakers largely replaced it with the native-derived yon in everyday counting. Shi survives in set phrases like shi-gatsu (April) and in rapid counting drills (ichi, ni, san, shi…). When in doubt, say yon.

How do I count past 100 in Japanese?

The same lego logic continues. 百 (hyaku) is 100, 千 (sen) is 1,000, and 万 (man) is 10,000. The one real adjustment is that Japanese groups large numbers in units of four digits rather than three, so 50,000 is go-man (“five ten-thousands”), not “fifty thousand”. Watch for sound changes too: 300 is sanbyaku, 600 is roppyaku, 800 is happyaku.

Are Japanese numbers written in kanji or Arabic numerals?

Both, and the choice depends on direction of writing. Horizontal text — websites, receipts, forms, most newspapers — overwhelmingly uses Arabic numerals. Vertical text such as novels, formal letters and some signage uses kanji numerals (一、二、三). You’ll read Arabic numerals far more often, but kanji numerals appear in prices at traditional shops, legal documents and dates, so both are worth recognising.

Numbers are the perfect thing to practise with a real person: they need speed, not just accuracy, and counters only stick once someone corrects you mid-sentence. Book a Japanese tutor with The Cognitio and spend your first lesson counting, ordering and telling the time out loud — you’ll be surprised how quickly 1 to 100 becomes automatic.