ASC in Excel: Convert Full-Width Text to Half-Width

=ASC(text)

text is required: supply a quoted text string or a reference to a cell containing text. There is no optional conversion mode or default argument. Microsoft documents ASC for double-byte character set (DBCS) languages, and says that text without full-width letters is unchanged. The documented use includes full-width English letters and Japanese katakana.

Width conversion is not translation, romanization, case conversion or a general Unicode cleanup operation. Do not assume that it converts every Chinese, Japanese or Korean character. Microsoft’s page does not give a complete conversion table for every language setting, nor does it state that a Japanese Office installation is always required. Check representative data in the environment where the workbook will be used.

Keep the original import in column A and put converted text in column B:

1. Put Half-width label in B1.
2. In B2, enter =ASC(A2).
3. Fill B2 down through B4.
4. Widen the columns so that both original and converted text can be inspected.

Expected B2 is NOTE. Expected B3 is ｶﾒﾗ in the documented Japanese-katakana use case. Expected B4 is Team, with its original capitalization. The formulas do not replace the values in A2:A4.

The first example maps the full-width letters Ｎ, Ｏ, Ｔ and Ｅ to N, O, T and E. The katakana example maps カ, メ and ラ to ｶ, ﾒ and ﾗ. These are character-mapping expectations, not screenshots or a claim that a particular Excel installation was tested. Fonts can make the distinction subtle: compare the actual strings, not just their appearance.

=ASC("ＮＯＴＥ")
=ASC("Team")

The expected results are NOTE and Team, respectively. Quotes delimit a literal string; omit the quotes when referring to a cell. Writing =ASC("A2") asks Excel to convert the two-character text A2 rather than the contents of cell A2.

ASC is a worksheet text function. It is different from VBA’s Asc function, which returns a character code. Microsoft’s WorksheetFunction.Asc documentation describes the worksheet conversion exposed to VBA. Do not apply VBA character-code examples or VBA’s empty-string error rules to this worksheet formula.

Suppose A2 contains ＮＯＴＥ and D2 contains NOTE. Put =ASC(A2) in B2, then use:

=EXACT(B2,D2)

Expected result: TRUE, because the normalized letters match exactly. If D2 instead contains Note, the expected comparison is FALSE: ASC has not changed case. See EXACT for case-sensitive comparisons and UPPER if a separate, deliberate case-standardization step is needed.

Keep normalization in a helper column while reviewing matches. Two distinct source labels can collapse to the same half-width label, so a normalized match is not proof that two customer, product or account records refer to the same entity. Preserve the original identifier and review duplicates before using converted labels as lookup keys.

Do not silently add other cleanup rules. Leading spaces, different punctuation, accented letters and voiced-kana combinations need separate evidence and tests. TRIM addresses its own documented space-cleanup problem; it is not a substitute for ASC. For the opposite width direction, consult DBCS and its language-specific behavior rather than assuming an unrestricted reversible conversion.

• Nothing changed: First check whether the source contains eligible full-width characters. Ordinary Team is supposed to remain unchanged. Also check that the formula references the intended cell.
• The text looks identical: Font rendering is not a reliable character comparison. Inspect the helper-column result and use an exact comparison against a known expected string.
• A lookup still fails: Width is only one possible difference. Case, spaces and unrelated characters are separate issues; identify them before adding transformations.
• An unexpected error appears: Microsoft does not publish an ASC-specific error table on the checked page. Check the source cell for an existing error and the formula for syntax problems, then reproduce the issue with a simple literal. Do not invent numeric error codes or assume undocumented blank-cell coercion.

Use commas in the English formulas shown here; some Excel locales use semicolons as argument separators.

The current Microsoft ASC reference, checked 19 October 2026, lists Excel for Microsoft 365 on Windows and Mac, Excel 2024 and 2021 on Windows and Mac, and Excel 2019 and 2016. These are documentation applicability labels, not a statement of vendor lifecycle support. The first release containing this function is not established here. The current English page does not list Excel for the web; that omission alone does not establish that web Excel lacks the function.

The examples in this guide are independently derived expectations based on the documented contract, not recorded Excel runs. No Excel version was available for native testing, and no screenshot is presented as execution evidence. Check the same examples in your actual Excel language and version before applying width conversion to a production dataset.