How do I convert a number to kanji?
Japanese counts in groups of four digits rather than three, using 万 for 10,000, 億 for 100,000,000 and 兆 for 1,000,000,000,000, so converting a number means grouping it by ten-thousands first, then writing each group with the digits 一 to 九 and the in-group units 十, 百, 千.
The formal daiji style (壱, 弐, 参, 拾, 萬) is required on financial documents and certificates in Japan to prevent a written number from being altered by adding a stroke — a simple 三 can be turned into another character far more easily than 参 can.
How do I convert 12345 to kanji numerals?
Split the number into groups of four digits from the right (ones/thousands, then ten-thousands, hundred-millions, and so on), convert each group using 一-九 with the in-group units 十/百/千, and attach the big-unit character (万/億/兆) to each non-final group. Example: 12345 splits into 1 (man-group) and 2345 (ones-group), giving 一万 + 二千三百四十五 = 一万二千三百四十五.
Steps to convert a number to standard kanji numerals
- Split the number into 4-digit groups from the right: ones (1-9999), 万 (10^4), 億 (10^8), 兆 (10^12).
- For each group, write the thousands digit + 千, hundreds digit + 百, tens digit + 十, and ones digit, omitting the digit itself when it's exactly 1 before 十/百/千 (十 not 一十, 百 not 一百, 千 not 一千).
- Attach the big-unit character to every non-empty group except the final (ones) group: 万 for the 10,000s group, 億 for the 100,000,000s group, 兆 for the 1,000,000,000,000s group.
- Unlike 十/百/千, always keep the leading digit before 万/億/兆 even when the group value is exactly 1 — write 一万, not just 万, for exactly 10,000.
- Concatenate the groups from largest to smallest, skipping any group that is entirely zero.
The three conversion modes
Digit-by-digit: each digit -> its kanji digit, no units (12345 -> 一二三四五) | Standard: 4-digit groups with 十百千 + 万億兆, omitting a leading 1 only before 十/百/千 (12345 -> 一万二千三百四十五) | Daiji: same grouping as standard but with tamper-resistant digits 壱弐参 and 十 -> 拾, 万 -> 萬, and the leading digit is never omitted (12345 -> 壱萬弐千参百四拾五)
- 万 = 10,000 (10^4), 億 = 100,000,000 (10^8), 兆 = 1,000,000,000,000 (10^12)
- Daiji digits: 壱=1, 弐=2, 参=3 (4-9 keep their ordinary form in common modern usage); 拾=10, 萬=10,000
Example conversions
| Number | Digit-by-digit | Standard | Daiji |
|---|
| 10 | 一〇 | 十 | 壱拾 |
| 100 | 一〇〇 | 百 | 壱百 |
| 1234 | 一二三四 | 千二百三十四 | 壱千弐百参拾四 |
| 12345 | 一二三四五 | 一万二千三百四十五 | 壱萬弐千参百四拾五 |
| 30000 | 三〇〇〇〇 | 三万 | 参萬 |
Frequently asked questions
Why is 10,000 written 一万 but 10 is just 十, not 一十?
Within a single 4-digit group, Japanese omits a leading "one" before 十/百/千 (10 is 十, 100 is 百, 1000 is 千). But the big units 万/億/兆 that join separate groups together always keep the explicit digit, so exactly 10,000 is written 一万, never just 万.
What is daiji and why does it use different characters?
Daiji (大字) is the formal numeral style required on Japanese financial documents, contracts and certificates. Its characters — 壱 instead of 一, 弐 instead of 二, 参 instead of 三, 拾 instead of 十 — are harder to alter with an extra stroke than the simple everyday numerals, which prevents tampering with amounts.
Does the daiji mode convert every digit to a special character?
This tool converts 1, 2, 3, 10 and 10,000 to their daiji forms (壱, 弐, 参, 拾, 萬), matching common modern Japanese usage on documents; digits 4 through 9 and the units 百/千 are commonly left in their ordinary form since they are not typically listed as required daiji substitutes.
What is the largest number this tool can convert?
This tool supports whole numbers up to just under 10 quadrillion (9,999 兆 9,999 億 9,999 万 9,999), covering all four grouping units through 兆 (10^12).
This tool converts non-negative whole numbers up to 9,999,999,999,999,999; it does not handle decimals, negative numbers, or classical/archaic daiji forms for digits 4-9 and the 百/千 units, which vary by document and era.