Full-width to Half-width: How to Convert Text

“All the letters in this form came out full-width and the layout looks broken.” “This CSV mixes full-width digits with half-width ones, so the system keeps rejecting it.” If you work with Japanese text, you have probably run into these situations. Japanese input environments produce both full-width and half-width characters, and mixing them makes documents look uneven and data harder to process.

In this guide, we explain the difference between full-width and half-width characters and how to convert text between the two forms. You will learn how to turn full-width letters and digits into half-width, how to convert half-width katakana back to full-width, what to watch out for, and how to use a free browser-based converter.

What is the difference between full-width and half-width?

Full-width and half-width describe the display width of characters. Full-width characters take up about twice the width of half-width ones.

Form	Example	What it covers
Full-width	ＡＢＣ, １２３, ！？, あいう	Full-width letters/digits/symbols, hiragana, katakana, kanji
Half-width	ABC, 123, !?, ｶﾀｶﾅ	Latin letters, digits, symbols, half-width katakana

In standard Japanese text, hiragana, katakana and kanji are full-width, while Latin letters and digits are half-width. Full-width Latin characters (ＡＢＣ, １２３) are usually the ones people want to convert back to half-width, especially for data entry and processing.

When do you need to convert?

Full-width/half-width conversion is useful in several everyday situations:

• Normalizing data entry: unify full-width letters and digits into half-width so search, matching and sorting work reliably
• Tidying up email and documents: clean up mixed-width text before sending or publishing
• Filling in forms: some systems require half-width input, and you may have typed full-width by accident
• Cleaning up CSV data: convert stray full-width digits or half-width katakana in exported data to match the target format
• Formatting posts and articles: keep Latin letters and digits in half-width for a cleaner look

How to convert full-width to half-width

The steps are simple:

1. Copy the text you want to convert
2. Paste it into the input area of a converter tool (see below)
3. Press the “To half-width” button
4. Copy the result and use it

For example, “ＡＢＣ１２３！？” becomes “ABC123!?”, and full-width spaces become half-width spaces. Hiragana and kanji are left untouched.

A note on katakana

Katakana also comes in two forms: full-width (カタカナ) and half-width (ｶﾀｶﾅ). Half-width katakana appears on receipts, in some system output, and in older mobile environments. The usual direction is half-width to full-width — converting those cramped half-width characters back to normal full-width katakana.

How to convert half-width to full-width

To convert in the other direction, press “To full-width”:

• “ABC123” becomes “ＡＢＣ１２３”
• “ｶﾀｶﾅ” becomes “カタカナ”, and voiced marks are combined correctly (“ｶﾞ” becomes “ガ”)

A converter tool handles combining voiced and semi-voiced marks automatically, so you do not need to fix each character by hand.

Things to watch out for

1. Hiragana and kanji are never converted

Conversion applies to Latin letters, digits, symbols, spaces and katakana. Hiragana and kanji stay exactly as they are.

2. Full-width and half-width spaces are different characters

A full-width space (　) and a half-width space ( ) may look similar, but they are separate characters in the data. Converting from full-width to half-width turns full-width spaces into half-width ones, and vice versa.

3. Your original text is never modified

When you use a converter tool, the input text is not rewritten. The result appears in a separate output area, so you can convert again as many times as you like without losing the original.

How to use the Tools Hub full-width/half-width converter

Doing this by hand is tedious for long passages. The Tools Hub converter transforms pasted text with a single click, and everything runs in your browser — your text is never sent to a server.

How to use it (three steps)

Summary

• Full-width characters are about twice as wide as half-width ones; Latin letters are typically half-width in Japanese text
• Full-width to half-width is used to normalize data entry and satisfy form requirements
• Half-width to full-width is used to restore regular katakana from receipts or system output
• Voiced and semi-voiced marks (ｶﾞ, ﾊﾟ) are combined and split automatically by the tool
• Hiragana and kanji are never converted; full-width and half-width spaces are different characters
• Your original text is never modified, so you can convert as often as you like

Full-width/half-width conversion is one of those small but essential chores in Japanese data work. With a converter tool you can align character widths in seconds, without mistakes. Paste your text and press a button — it is that simple.

FAQ

What is the difference between full-width and half-width?

Full-width characters are displayed at about twice the width of half-width ones. Latin letters, digits, symbols and spaces come in both forms (ＡＢＣ, １２３ vs ABC, 123), and katakana does too (ｶﾀｶﾅ vs カタカナ).

How do I convert full-width letters and digits to half-width?

Paste the text into the converter’s input area and press “To half-width”. Full-width letters, digits, symbols and spaces are converted, and you can copy the result.

Can I convert half-width katakana to full-width?

Yes. Half-width katakana (ｶﾀｶﾅ) is converted to full-width katakana (カタカナ), with voiced and semi-voiced marks (ｶﾞ, ﾊﾟ) combined correctly.

Does conversion affect hiragana or kanji?

No. Conversion applies to Latin letters, digits, symbols, spaces and katakana only. Hiragana and kanji are left unchanged.

References

• Full-width and half-width forms (Wikipedia)
• Unicode block: Halfwidth and Fullwidth Forms
• String.prototype.normalize() (MDN Web Docs)