Write a number in kanji — standard and formal daiji

The job

Two situations come up most: writing an amount on a Japanese form that expects kanji, and reading a kanji amount from an old document. Formal paperwork often demands daiji (壱弐参…) precisely because the characters are hard to alter — 一 could become 十 with a single added stroke.

How to do it

Choose the direction — digits to kanji or kanji to digits. For digits to kanji, pick standard (一万二千三百四十五) or formal/daiji (壱万弐千参百四拾五) style, convert, and copy the result you need. For kanji to digits, paste the numeral as written — both standard and daiji characters are recognized.

• Standard style drops the leading 一 before 十・百・千, so 1200 renders 千二百, matching everyday writing.
• Daiji maps each digit to its formal counterpart and units to 拾・佰・阡・萬.
• Mixed input like 一万2千三百 works in the reverse direction.

Worked example

Writing an invoice total of 51,234 yen in formal style: enter 51234, pick daiji, and get 伍萬壱阡弐佰参拾肆 — paste it into the contract field. Reading an old ledger entry 参阡伍佰 is the same tool in reverse: 3,500.

Limits

Integers only — decimals and fractions are not kanji-native in this style. The range tops out at 9999京 (just under 10^20); larger values are rejected rather than guessed at. Positional notation such as 一〇二 (years, phone digits) is a different convention and is not parsed.