Katakana is one of Japan’s two kana syllabaries, used chiefly for loanwords, foreign names, technical terms, and emphasis. It mirrors Hiragana syllable for syllable but has its own angular glyphs. This free tool applies the standard Hepburn romanisation in both directions — Katakana to Romaji and back — instantly and with no upload.
How it works
Converting Katakana to Romaji, the tool matches the longest unit first so contracted sounds (yōon) like キャ read as the single syllable kya. The small ッ (sokuon) doubles the consonant that follows it, and the long-vowel mark ー (chōonpu) repeats the previous vowel, so コーヒー becomes koohii.
Converting Romaji to Katakana, the tool greedily matches the longest valid syllable at each position, recognising shi, chi, tsu, kya, and nn before single letters. A doubled consonant becomes a small ッ before the syllable, and a trailing n becomes ン.
Tips and notes
Hepburn writes シ as shi, ジ as ji, チ as chi, ツ as tsu, and フ as fu; use those spellings when typing Romaji for the cleanest round-trip. Because katakana often spells loanwords, long vowels are common — expect the ー mark when going back from doubled Romaji vowels. Unrecognised characters such as kanji, punctuation, and spaces pass through unchanged. Everything runs locally in your browser — your text is never sent to a server.