Corporate Numbers, full/half-width, postal codes, katakana and JIS levels — the conversions and checks Japanese work needs, in one place.
A Corporate Number is 13 digits: a check digit prefixed to the 12-digit base number. Enter 12 digits to compute the full 13, or 13 digits to validate. The check-digit formula is the National Tax Agency's published method. Registered details can be searched on theNTA Corporate Number Publication Site.
Alphanumerics and symbols convert both ways between full-width (Ａ１！ etc.) and half-width; katakana converts between half-width kana (including voiced combinations like ｶﾞ) and full-width kana.
Postal data is queried via zipcloud's public API (this is the only feature that makes a request). Some codes, such as business-specific ones, return multiple candidates.
Covers: hiragana → katakana, romaji (Hepburn) → katakana, digits & Latin letters → katakana readings. Kanji are left as-is (no reading guesses).
Classification follows JIS X 0208 ward numbers (wards 16–47 = Level 1, 2,965 characters; wards 48–84 = Level 2, 3,390 characters). “Convert” replaces Level-2 and non-JIS kanji with 〓 and counts the replacements. Level 2 is common in names and place names, so check the content before applying.