Can ASC be used to convert Japanese Katakana to Roman letters?

No. ASC only changes character width; it does not perform transliteration. To convert Katakana to Roman letters you would need a custom mapping or a language-specific function, not ASC.

Why does ASC return the same string when the input is already ASCII?

ASC only modifies full-width characters. If the input contains only standard half-width ASCII characters, there is nothing to change, so the function returns the original text unchanged.

Does ASC work on whole columns or arrays?

ASC expects a single text value. Supplying a range returns #VALUE! because the function cannot process multi-cell arrays directly. Use BYROW or BYCOL to apply ASC to each cell individually.

How does ASC differ from the TEXT function?

TEXT formats numbers according to a pattern; ASC normalizes character width. They serve different purposes: TEXT for number-to-string conversion, ASC for character-set cleanup.

ASC function

ASC converts full-width (double-byte) characters in a text string to their single-byte ASCII equivalents, returning a normalized plain-text result.

=ASC(text)

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Describe what you need. The generator will reach for ASC where ASC is the right tool, and tell you when it is not.

Arguments

How ASC reads its arguments

Argument	Required	Description
text	Required	A required text argument; if omitted or non-text, Excel coerces or returns #VALUE! for unsupported characters.

Returns

ASC returns a single-cell text string of the same size as the input.

Availability

Excel: All · Google Sheets: Supported

Worked examples

1. Normalize SKU codes

SKU	Warehouse	On Hand	Reorder Point	Cost
ＡＢＣ123	East	50	30	15.00

=ASC(A2)

Result: ABC123

The SKU in A2 contains full-width letters ＡＢＣ. ASC converts each of those to their half-width counterparts, producing the plain-text code ABC123. This is useful when matching SKU values against external systems that expect standard ASCII.

2. Standardize warehouse names for lookup

SKU	Warehouse	On Hand	Reorder Point	Cost
XYZ789	Ｎｏｒｔｈ	20	15	8.50

=ASC(B2)

Result: North

The warehouse name in B2 is stored with full-width characters (Ｎｏｒｔｈ). ASC strips the double-byte formatting, yielding the regular string North. After conversion you can safely use VLOOKUP or XLOOKUP against a list that contains plain-text region names.

3. Convert full-width cost strings to numbers

SKU	Warehouse	On Hand	Reorder Point	Cost
LMN456	West	75	40	１５．００

=ASC(E2)

Result: 15.00

The cost in E2 uses full-width digits and a full-width period (１５．００). ASC changes them to ordinary ASCII digits and a period, producing the text "15.00". You can then wrap the result in VALUE() to turn it into a numeric value for calculations.

Common errors

Which ASC error are you seeing?

Error	Why it happens	How to fix it
#VALUE!	The text argument contains characters that have no half-width equivalent, such as emojis or certain Asian punctuation.	Remove or replace those characters with SUBSTITUTE before calling ASC, or use CLEAN to strip non-printable symbols.
#N/A	The referenced cell itself contains the #N/A error, which propagates through ASC because it cannot operate on an error value.	Wrap the reference in IFNA or IFERROR to supply a fallback string before applying ASC.
#REF!	The formula points to a cell that has been deleted or to an invalid range, causing a reference error.	Correct the cell reference so it points to an existing cell that contains the text you wish to normalize.

Tips and when to use something else

Use CLEAN first if you suspect hidden control characters that ASC will ignore.
Combine ASC with SUBSTITUTE when you need to replace a specific full-width symbol with something else.
If you only need to change case, use UPPER, LOWER, or PROPER instead of ASC.
For numeric conversion after ASC, wrap the result in VALUE() to get a true number.

Related functions

CLEANCLEAN removes all non-printing characters (ASCII 0–31) from a text string, returning a clean version suitable for further processing or display.SUBSTITUTESUBSTITUTE returns a new text string where specified characters or substrings are replaced, optionally limiting the change to a particular occurrence.TEXTTEXT converts a numeric, date, or time value into a formatted text string based on a custom format pattern you supply.VLOOKUPVLOOKUP searches the first column of a table and returns a value from a specified column in the same row, optionally using exact or approximate matching.XLOOKUPXLOOKUP returns the value from a specified return array that corresponds to a given lookup value, with optional handling for missing matches and search direction.

Frequently asked questions

Can ASC be used to convert Japanese Katakana to Roman letters?: No. ASC only changes character width; it does not perform transliteration. To convert Katakana to Roman letters you would need a custom mapping or a language-specific function, not ASC.
Why does ASC return the same string when the input is already ASCII?: ASC only modifies full-width characters. If the input contains only standard half-width ASCII characters, there is nothing to change, so the function returns the original text unchanged.
Does ASC work on whole columns or arrays?: ASC expects a single text value. Supplying a range returns #VALUE! because the function cannot process multi-cell arrays directly. Use BYROW or BYCOL to apply ASC to each cell individually.
How does ASC differ from the TEXT function?: TEXT formats numbers according to a pattern; ASC normalizes character width. They serve different purposes: TEXT for number-to-string conversion, ASC for character-set cleanup.

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Reviewed 2026-09-17