Convert Excel to XLS — Free Online Converter
Convert Microsoft Excel (.excel) 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 .xlsx 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 XLSX to XLS Conversion
Users searching for "Excel to XLS" typically have a modern .xlsx spreadsheet that needs to be downgraded to the legacy .xls binary format (Word 97-2003 BIFF8) for compatibility with older systems. This conversion takes any Excel file and produces the XLS binary format that works with every version of Excel from 1997 onward, including legacy enterprise software, industrial control systems, and automated import processes that were built before the XLSX format existed in 2007.
The XLS format uses the Binary Interchange File Format (BIFF8) with OLE2 compound document structure. While technically outdated, it remains deeply embedded in enterprise workflows worldwide — ERP modules, legacy accounting packages, government systems, and factory automation controllers that were programmed to read XLS continue to operate and require this specific binary format.
Why Convert XLSX to XLS?
Many industrial and enterprise systems were built before 2007 and have never been updated. ERP modules, inventory management systems, and custom reporting tools that accept Excel input were often programmed specifically for the BIFF binary format. These systems cannot parse XLSX's XML structure. Converting to XLS is the only way to feed modern spreadsheet data into these older pipelines.
Some organizations maintain XLS as their standard for maximum backward compatibility. Manufacturing plants running Office 2003, healthcare facilities with locked-down IT, and government offices with legacy systems all require XLS format to ensure files open without compatibility warnings or format conversion prompts.
Common Use Cases
- Feed modern Excel data into legacy ERP systems that only accept XLS binary format
- Share spreadsheets with colleagues using Microsoft Office 2003 or earlier
- Prepare data exports for industrial control systems with hardcoded XLS import routines
- Generate XLS files for automated workflows that parse the BIFF binary format directly
- Ensure compatibility with legacy accounting and inventory management software
How It Works
LibreOffice opens the Excel file (detecting XLSX or XLS input automatically) in headless mode and re-serializes the workbook as a BIFF8 binary file. Cell values, formulas (translated to BIFF syntax), number formats, cell styles, column widths, row heights, sheet names, and basic chart objects are mapped to their XLS equivalents. Data exceeding XLS limits is handled gracefully: rows beyond 65,536 and columns beyond 256 (IV) are truncated.
Quality & Performance
Standard cell data and formatting convert accurately. Features exclusive to XLSX — such as tables (ListObjects), slicers, dynamic array formulas, Power Query, and icon-set conditional formatting — are either simplified or removed because they have no BIFF8 equivalent. Conditional formatting is limited to three rules per range. VBA macros are stripped since the source is typically a macro-free XLSX.
Device Compatibility
| Device | XLSX | 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
- 1Check row counts before converting — data beyond row 65,536 will be silently truncated
- 2Replace dynamic array formulas with static values (paste as values) before converting
- 3Remove Table formatting and convert to regular cell ranges before downgrading to XLS
- 4Test the XLS output in the target legacy system to verify formatting compatibility
- 5Keep the original XLSX as the master copy — XLS is a reduced-feature derivative
Related Conversions
Excel-to-XLS conversion provides backward compatibility for legacy systems that require the older binary format, at the cost of modern features and expanded data capacity.