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.
Where Katakana is used
Understanding when to expect Katakana helps you use this tool more effectively:
- Loanwords (gairaigo): Words borrowed from English and other languages are nearly always written in Katakana. For example, コーヒー (koohii) from “coffee,” テレビ (terebi) from “television,” and コンピューター (konpyuutaa) from “computer.”
- Foreign names: People and place names from outside Japan are written in Katakana. メアリー (Mearii) for “Mary,” ロンドン (Rondon) for “London.”
- Technical and scientific terms: Many scientific words, brand names, and technical jargon use Katakana.
- Onomatopoeia and sound effects: Manga and comics use Katakana for dramatic sound words.
- Emphasis: Native Japanese words can be written in Katakana for stylistic effect, similar to italics in English.
Common Hepburn spellings to know
Hepburn romanisation has a few spellings that differ from what English speakers might expect:
| Katakana | Hepburn | Note |
|---|---|---|
| シ | shi | not “si” |
| チ | chi | not “ti” |
| ツ | tsu | not “tu” |
| フ | fu | not “hu” |
| ジ | ji | not “zi” |
| ヅ | zu | same as ズ |
Use these exact spellings when typing Romaji into the tool for a clean round-trip conversion.
Handling long vowels
Long vowels are especially common in Katakana because many English loanwords have long syllables. The katakana chōonpu ー stretches the preceding vowel. In Hepburn, this is written by repeating the vowel letter: ー after コ gives oo, so コーヒー = koohii. When converting back from Romaji, type the doubled vowel and the tool will produce the ー mark.
Tips and notes
Unrecognised characters such as kanji, punctuation, and spaces pass through unchanged, so you can safely paste mixed Japanese text and the tool will convert only the Katakana portions. Everything runs locally in your browser — your text is never sent to a server.