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ASC Function (LibreOffice Calc)

Text Beginner LibreOffice Calc Introduction not established

The ASC function converts full-width (double-byte) characters to half-width (single-byte) characters. It is primarily used for Japanese and East Asian text normalization.

Verification status: Consult the documentation, examples and any stated test scope below. How formula examples are checked

Availability and version history

  • Introduced: Documented by LibreOffice 26.8.1.1; original introduction not established.
  • Availability: Supported in LibreOffice 26.8.1.1, verified against its function registry. This identifies a supported release, not a final working version.
  • Scope: Desktop Calc, using the English function name. Availability in other spreadsheet applications is separate.
  • Checked: 2026-10-14 — function reference; versioned support. Documentation/source check; not a new native test. Existing example-specific test claims below retain their stated scope.
The **ASC** function converts **full-width (double-byte)** characters to **half-width (single-byte)** characters. It is primarily used in Japanese and East Asian text processing, where characters may appear in multiple width forms.

What the ASC Function Does

  • Converts full-width characters → half-width
  • Normalizes Japanese and East Asian text
  • Useful for data cleaning, imports, and text comparison
  • Complements the JIS function (half-width → full-width)

Syntax

ASC(text)

Arguments

  • text:
    A string containing characters to convert.

Basic Examples

Convert full-width English letters

=ASC("ＡＢＣ")
→ "ABC"

Convert full-width numbers

=ASC("１２３４")
→ "1234"

Convert full-width punctuation

=ASC("！＠＃")
→ "!@#"

Using a cell reference

=ASC(A1)

Advanced Examples

Normalize imported Japanese text

=ASC(A1)

Combine with JIS for round-trip conversion

=JIS(ASC(A1))

Normalize before comparison

=ASC(A1)=ASC(B1)

Clean mixed-width product codes

=ASC(SUBSTITUTE(A1; "－"; "-"))

Normalize before VLOOKUP

=VLOOKUP(ASC(A1); ASC(Table); 2; 0)

Convert only part of a string

=LEFT(ASC(A1); 5)

Edge Cases and Behavior Details

ASC returns a text string

Accepts:

  • Any text
  • Mixed-width strings
  • Unicode characters

Behavior details

  • Only characters with full-width equivalents are converted
  • Non-convertible characters remain unchanged
  • Works with Japanese kana, ASCII, numbers, and punctuation
  • Does not convert kanji (漢字) — they are already full-width
  • Useful for DBCS (double-byte character set) environments

Invalid input → Err:502 (rare)

ASC of an error → error propagates

Common Errors and Fixes

Unexpected characters remain unchanged

Cause:

  • Character has no half-width equivalent
  • Kanji or symbols that do not map to ASCII

Fix:

  • Use SUBSTITUTE for custom mappings
  • Use UNICODE/UNICHAR for manual conversions

VLOOKUP mismatch

Cause:

  • One value is full-width, the other half-width

Fix:

  • Normalize both sides with ASC

Best Practices

  • Always normalize imported Japanese/East Asian text
  • Use ASC before comparisons, lookups, and joins
  • Combine with JIS for full-width ↔ half-width workflows
  • Use LENB, LEFTB, MIDB, RIGHTB for byte-aware operations
  • Use CLEAN to remove control characters after conversion
ASC is your full‑width → half‑width normalization engine — essential for Japanese text cleaning, imports, and reliable comparisons.
  • Use JIS to convert half-width → full-width
  • Use UNICODE and UNICHAR for precise character control
  • Use LENB, LEFTB, MIDB, RIGHTB for byte-level operations
  • Use CLEAN and TRIM for text sanitization

By mastering ASC and its companion functions, you can build robust, reliable, and fully normalized text-processing workflows in LibreOffice Calc.