Convert CSV to XLS — Free Online Converter
Convert Comma-Separated Values (.csv) to Microsoft Excel Spreadsheet (.xls) online for free. Fast, secure document conversion with no watermarks or registration.
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How to Convert
Upload your .csv file by dragging it into the upload area or clicking to browse.
Choose your output settings. The default settings work great for most files.
Click Convert and download your .xls file when it's ready.
About CSV to XLS Conversion
CSV stores tabular data as plain text with comma-delimited values — universally portable but devoid of formatting, formulas, or data types. XLS is the legacy binary spreadsheet format used by Microsoft Excel from version 97 through 2003. While superseded by XLSX, the XLS format remains necessary for compatibility with older systems, legacy macros, and enterprise software that was never updated to support the newer Open XML standard.
Converting CSV to XLS produces a binary Excel workbook that can be opened by every version of Excel ever released, as well as LibreOffice, OpenOffice, and Google Sheets. This conversion is specifically needed when downstream systems or recipients require the older XLS format rather than the modern XLSX.
Why Convert CSV to XLS?
Legacy enterprise systems in manufacturing, healthcare, finance, and government often mandate XLS format for data imports. ERP systems like older versions of SAP, Oracle, and custom-built tools from the early 2000s frequently accept only XLS files. Automated workflows that were built around the XLS format continue to run in production at thousands of organizations worldwide.
Additionally, some regulatory filings, government data submissions, and industry-specific software still require XLS format explicitly. Converting CSV data to XLS ensures compatibility with these legacy requirements without manual data entry, while also gaining the benefit of native Excel data types (numbers, dates) over CSV's plain text representation.
Common Use Cases
- Import CSV data into legacy ERP systems that accept only XLS format for data ingestion
- Convert database CSV exports to XLS for upload to regulatory reporting platforms that mandate the older format
- Transform CSV time-tracking data into XLS for payroll systems built on Excel 97-2003 templates
- Prepare CSV product data as XLS files for retail partners using legacy inventory management software
- Convert CSV financial data to XLS for compatibility with older audit tools and macros
How It Works
LibreOffice parses the CSV data, detecting delimiters, text encoding, and column data types. The data is written into XLS format using the BIFF8 binary specification (Binary Interchange File Format version 8, used by Excel 97-2003). XLS stores data in a compound OLE2 file with binary records for cell values, formatting, and workbook structure. Numeric values are stored as IEEE 754 double-precision floats, dates as serial numbers with date formatting flags, and text as unicode strings. The XLS format supports up to 65,536 rows and 256 columns per worksheet.
Quality & Performance
All CSV data is accurately preserved in the XLS output with correct column alignment and data types. The primary limitation is XLS's row/column capacity: maximum 65,536 rows and 256 columns. CSV files exceeding these limits will be truncated. For datasets beyond XLS limits, use the CSV-to-XLSX converter instead (which supports 1,048,576 rows and 16,384 columns). Unicode text, special characters, and multi-byte encodings are fully supported within the XLS format's capabilities.
Device Compatibility
| Device | CSV | XLS |
|---|---|---|
| Windows PC | Partial | Partial |
| macOS | Partial | Partial |
| iPhone/iPad | Partial | Partial |
| Android | Partial | Partial |
| Linux | Partial | Partial |
| Web Browser | No |
Tips for Best Results
- 1Only use XLS if your target system specifically requires it — XLSX is better for all modern workflows
- 2Check that your CSV has fewer than 65,536 rows and 256 columns to avoid data truncation in the XLS format
- 3Use UTF-8 encoding in your CSV for reliable handling of international characters in the XLS output
- 4Include a header row to clearly label columns in the resulting spreadsheet
- 5Test the XLS output in the specific legacy application that will consume it to verify compatibility
Related Conversions
CSV-to-XLS conversion produces legacy-compatible Excel workbooks for systems and workflows that require the binary BIFF8 format, ensuring data compatibility with older software.