Converting Excel (XLSX) to CSV should be simple, but it is riddled with pitfalls that can silently corrupt your data. Leading zeros disappear, dates change format, special characters break, and formulas become literal text. This guide explains what happens during conversion and how to avoid common problems.
What Gets Lost in Conversion
| Excel Feature | Preserved in CSV? | Impact |
|---|---|---|
| Cell values | Yes | Raw values are preserved |
| Formulas | Results only | Formula logic is lost; only calculated values remain |
| Formatting (bold, colors) | No | All visual formatting is stripped |
| Multiple sheets | No | CSV supports one sheet only |
| Charts and images | No | Completely removed |
| Data types (date, number) | No | Everything becomes text in CSV |
| Cell comments | No | Removed |
| Merged cells | No | Only first cell retains the value |
Common Pitfalls
1. Leading Zeros Disappear
ZIP codes (07001), product codes (00123), and phone numbers lose leading zeros when opened in Excel because Excel interprets them as numbers. To preserve: format the column as Text before pasting, or prefix with an apostrophe.
2. Date Format Mangling
Excel stores dates as serial numbers internally. When exporting to CSV, the date format depends on locale settings. "01/02/2026" could mean January 2 (US) or February 1 (EU). Always specify ISO 8601 format (YYYY-MM-DD) for unambiguous dates.
3. Encoding Issues (UTF-8 BOM)
Excel defaults to the system locale encoding. Non-ASCII characters (é, ü, 漢字) may break in CSV if not saved as UTF-8. When opening UTF-8 CSVs in Excel, the BOM (Byte Order Mark) helps Excel detect the encoding. UTF-8 with BOM is recommended for Excel compatibility.
4. Delimiter Confusion
Some European locales use semicolons (;) instead of commas as the CSV delimiter because commas are used as decimal separators. When sharing CSVs internationally, specify the delimiter explicitly or use tab-separated values (TSV).
5. Multi-Sheet Handling
CSV supports only one table. For multi-sheet workbooks, export each sheet as a separate CSV file, or merge sheets into one before exporting.
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