Convert XLS to Excel — Free Online Converter
Convert Microsoft Excel Spreadsheet (.xls) to Microsoft Excel (.excel) online for free. Fast, secure document conversion with no watermarks or registration.
Secure Transfer
HTTPS encrypted uploads
Privacy First
Files auto-deleted after processing
No Registration
Start converting instantly
Works Everywhere
How to Convert
Upload your .xls 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 .xlsx file when it's ready.
About XLS to XLSX Conversion
XLS is the legacy binary spreadsheet format from Microsoft Excel 97-2003, using the Binary Interchange File Format (BIFF8). The modern Excel format (XLSX) uses Open XML, a ZIP-compressed collection of XML files standardized as ISO/IEC 29500. Converting XLS to the modern Excel format upgrades the file from the proprietary binary structure to the open, XML-based container that current versions of Excel, Google Sheets, and LibreOffice expect.
This conversion preserves cell values, basic formulas, number formatting, column widths, and sheet names while migrating the underlying storage format. The resulting file is smaller due to ZIP compression, more resilient to corruption, and fully compatible with collaboration features in Microsoft 365 and Google Workspace.
Why Convert XLS to XLSX?
Microsoft deprecated the XLS format with Office 2007, and modern Excel versions display a compatibility warning when opening XLS files. Features like tables, sparklines, conditional formatting rules beyond three, and worksheets with more than 65,536 rows are unavailable in the legacy format. Converting to the modern format unlocks these capabilities and removes the compatibility barrier.
Organizations maintaining archives of XLS files from the early 2000s face increasing risk as fewer applications support BIFF8 parsing. Converting to the modern format future-proofs the data while reducing file sizes by 30-50% through ZIP compression, saving storage and speeding up email attachments.
Common Use Cases
- Upgrade archived Excel 97-2003 files for use in Microsoft 365
- Prepare legacy XLS reports for editing in Google Sheets
- Reduce file sizes of bulk XLS archives through modern compression
- Enable collaboration features unavailable in the legacy XLS format
- Migrate XLS files to SharePoint document libraries that prefer XLSX
How It Works
The conversion engine uses LibreOffice in headless mode to parse the XLS BIFF8 binary records, reconstruct the workbook in memory, and re-serialize it as an Open XML package. Cell values, formulas, number formats, cell styles, column widths, row heights, sheet names, and print settings are mapped to their OOXML equivalents. VBA macro code is not carried over because XLSX does not support macros — use XLSM if macros are needed.
Quality & Performance
Cell data and basic formatting transfer accurately. Simple formulas using standard Excel functions convert without issues. Complex VBA macros, ActiveX controls, and OLE embedded objects are not preserved in the XLSX output. Conditional formatting rules and pivot tables may require minor manual adjustment after conversion. Chart appearance is generally maintained, though some legacy chart subtypes may render slightly differently.
Device Compatibility
| Device | XLS | XLSX |
|---|---|---|
| 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 for VBA macros before converting — switch to XLSM format if macros must be preserved
- 2Verify pivot table functionality after conversion, as some legacy pivot cache structures may need refreshing
- 3Convert large XLS archives in batch to save significant storage space through XLSX compression
- 4Open the converted file in Excel and recalculate all formulas (Ctrl+Alt+F9) to confirm correctness
- 5Review conditional formatting rules after conversion, especially those with more than three conditions
Related Conversions
XLS to modern Excel conversion upgrades legacy spreadsheets to the current Open XML standard, reducing file size, improving compatibility, and unlocking modern spreadsheet features.