The Excel ASC function converts full-width (double-byte, zenkaku) characters to half-width (single-byte, hankaku). In Japanese and other East Asian documents, the digits １２３ and letters ＥＸＣＥＬ are different characters from 123 and EXCEL — they look wider, they don’t match in lookups, and full-width “numbers” won’t sum. ASC normalises them all to their regular half-width forms in one pass. Its mirror image is DBCS, which widens text back.
VALUE if the result should be a real number: =VALUE(ASC(A2)).
Syntax
| Argument | Description | |
|---|---|---|
text | Required | The text to convert, or a cell reference. Full-width letters, digits, punctuation, spaces, and katakana become half-width; everything already half-width — and kanji, which have no half-width form — passes through untouched. |
Available in: all Excel versions. The conversion does real work when an East Asian language (Japanese, Chinese, Korean) is enabled in Office; otherwise Excel has no width pairs to map and ASC returns the text unchanged — it never errors out.
Normalising imported Japanese data
Typical cleanup after a Japanese export — product codes, percentages, and katakana arrive full-width and refuse to match anything typed on a Western keyboard:
| A | B | C | |
|---|---|---|---|
| 1 | Full-width input | =ASC(A2) | What changed |
| 2 | ＥＸＣＥＬ１２３ | EXCEL123 | letters & digits narrowed |
| 3 | １００％ | 100% | digits and % narrowed |
| 4 | トウキョウ | ﾄｳｷｮｳ | katakana to half-width form |
Full-width digits are text, so they break SUM. Narrow them, then convert to numbers:
For lookups against a half-width master list, wrap the dirty side only:
Try it: interactive ASC demo
Type or paste text with full-width characters and watch ASC narrow it. Try mixing widths: ＭＳ Office ２０２６
Errors & common pitfalls
Pitfall: nothing happens on a Western-language system. Without East Asian language support enabled in Office, ASC returns its input unchanged — no error, no warning. The formula isn’t broken; the conversion tables simply aren’t loaded. (Most full-width Latin characters still convert on modern Excel, but don’t count on katakana handling without Japanese support.)
Pitfall: the result is still text. =ASC("１２３") returns the text "123", not the number 123. Wrap with VALUE before doing arithmetic.
Pitfall: kanji are untouched — by design. Kanji and hiragana have no half-width forms, so ASC leaves them alone. Only Latin letters, digits, punctuation, spaces, and katakana change width.
Pitfall: half-width katakana in output. ASC converts full-width katakana to the cramped half-width katakana of legacy systems. If you want narrow Latin characters but normal-width katakana, run ASC first and then DBCS on the katakana portions — or handle katakana separately.
Practice workbook
Frequently asked questions
What's the difference between ASC and DBCS?
Why doesn't ASC change my text?
Why won't my imported Japanese numbers add up, and does ASC fix it?
=VALUE(ASC(A2)). Copy the helper column, paste as values, and your totals come alive.Master functions like this in one day
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