Number ↔ Kanji Numeral Converter
Convert between Arabic numerals and Japanese kanji numerals. Supports both simple digit-by-digit substitution (一二三) and standard positional notation using 十/百/千/万/億 (百二十三).
Digit-to-kanji reference table
| Digit | Kanji |
|---|---|
| 0 | 〇 |
| 1 | 一 |
| 2 | 二 |
| 3 | 三 |
| 4 | 四 |
| 5 | 五 |
| 6 | 六 |
| 7 | 七 |
| 8 | 八 |
| 9 | 九 |
Positional unit reference table
| Unit | Value | Note |
|---|---|---|
| 十 | 10 | Written as 十, not 一十 |
| 百 | 100 | Written as 百, not 一百 |
| 千 | 1,000 | Written as 千, not 一千 |
| 万 | 10,000 | Written as 一万, not 万 — the opposite rule from 十/百/千 |
| 億 | 100,000,000 | Written as 一億, not 億 |
| 兆 | 1,000,000,000,000 | Written as 一兆, not 兆 |
Tips
- The "positional notation" mode reproduces the formal kanji numerals actually used in Japanese writing and documents, such as 百二十三 for 123.
- The leading 一 (one) is dropped right before 十/百/千, but kept before 万/億/兆 (e.g. 1,000 → 千, but 10,000 → 一万). This asymmetric rule trips up even native Japanese speakers.
- The "simple digit substitution" mode is handy when you just want to read out a sequence of digits, like a phone number, one by one (e.g. 123 → 一二三).
- When converting kanji to a number, any character outside 〇–九 and 十/百/千/万/億/兆 will cause an error, so don't mix in full-width digits or Arabic numerals.
- The positional mode supports 0 through 9,999,999,999,999 (up to the 兆 / trillion place).
Frequently Asked Questions
Side Note — Why Japanese groups numbers by 万 (10,000)
Western number systems, including English, group digits every 1,000: thousand, million, billion, each a thousand times the last. Japanese (along with Chinese, Korean, and other cultures that adopted Chinese characters) instead groups every 10,000: after 千 (thousand) comes 万 (10,000), then 億 (100,000,000). Because these grouping boundaries don't line up, converting large numbers between English and Japanese notation is a common source of confusion, especially for translators and international business.
This "myriad grouping" system, called 万進法 in Japanese, traces back to ancient Chinese numeral systems and was transmitted to Japan along with Chinese characters. It remains deeply embedded in everyday Japanese life — national budget figures, for instance, are almost always reported in 兆円 (trillion yen) or 億円 (hundred-million yen) rather than being translated into millions or billions.
There is also a separate, rarely-discussed set of kanji numerals called daiji (大字): 壱, 弐, 参 instead of 一, 二, 三. These are used specifically on financial documents like invoices, receipts, and contracts as a forgery-prevention measure — a single extra stroke could turn 一 into 二 or 三, but the more complex daiji characters are far harder to alter undetected. Traces of this convention survive today, for example on the decorative envelopes used for cash gifts in Japan, which are often inscribed with amounts like 金参万円也 using daiji.