Convert XLS to XLSX Online Free
Upgrade legacy Excel .xls files to the modern .xlsx format. Preserve your data while moving to the open XML-based format that all current spreadsheet apps support.
To convert XLS to XLSX, drop your legacy Excel file onto the ChangeThisFile converter. The old binary format is read and re-saved as a modern XLSX file with your data preserved. Free, browser-based, no Excel needed, and your spreadsheet never leaves your device.
Convert XLS to XLSX
Drop your XLS file here to convert it instantly
Drag & drop your .xls file here, or click to browse
Convert to XLSX instantly
XLS vs XLSX: Format Comparison
Key differences between the two formats
| Feature | XLS (Excel Legacy) | XLSX (Excel Spreadsheet) |
|---|---|---|
| File format | Binary BIFF (proprietary) | Open XML (ZIP with XML inside) |
| Introduced | Excel 97 (1997) | Excel 2007 |
| Max rows | 65,536 | 1,048,576 |
| Max columns | 256 (A-IV) | 16,384 (A-XFD) |
| File size | Often larger for same data | Compressed, typically smaller |
| Security | Macro code can hide in binary | Macros separated into .xlsm files |
| Modern support | Legacy, limited in newer tools | Standard format for all modern apps |
When to Convert
Common scenarios where this conversion is useful
Upgrading archived spreadsheets
Convert old .xls archives to .xlsx for better compatibility with modern Excel, Google Sheets, and LibreOffice Calc.
Overcoming row limits
XLS files are limited to 65,536 rows. Converting to XLSX allows the spreadsheet to be extended to over 1 million rows in modern Excel.
Improving file sharing compatibility
Some modern tools and cloud services no longer support .xls uploads. Convert to .xlsx for universal compatibility.
Reducing file sizes
XLSX uses ZIP compression, often resulting in smaller files than the equivalent XLS binary format.
Security compliance
Organizations phasing out legacy formats for security reasons can batch-convert XLS archives to the safer XLSX format.
How to Convert XLS to XLSX
-
1
Upload your XLS file
Drag and drop your .xls file onto the converter, or click to browse. Excel 97-2003 binary format is fully supported.
-
2
Automatic conversion
Your legacy spreadsheet is parsed in the browser. Data, formulas (as values), and cell content are read from the binary format and rewritten as XLSX.
-
3
Download the XLSX result
Click Download to save your modern .xlsx file. Open it in Excel 2007+, Google Sheets, or LibreOffice Calc.
Frequently Asked Questions
Basic cell values and data types are preserved. Complex formatting like conditional formatting, macros, and VBA code are not carried over in this conversion.
Formulas are resolved to their last computed values. The XLSX output contains the calculated results rather than the formula expressions.
The converter processes the first sheet. For multi-sheet workbooks, convert each sheet separately or use desktop Excel for full workbook conversion.
Excel 97, 2000, XP (2002), and 2003 .xls files are supported. These all use the BIFF8 binary format.
Yes. Google Sheets fully supports .xlsx files. Upload the converted file to Google Drive and open it directly.
No. VBA macros in XLS files are not carried over. The output is a standard .xlsx file (not .xlsm). Extract macro code separately if needed.
No. The converter uses SheetJS to read XLS and write XLSX entirely in your browser. No Office installation is required.
Dates are preserved as their formatted text representation. Excel serial date numbers are converted to readable date values.
No. Password-protected or encrypted XLS files cannot be read by the browser-based parser. Remove the password first.
Yes. The conversion runs entirely in your browser. Your spreadsheet data is never uploaded to any server.
Related Conversions
Ready to convert your file?
Convert XLS to XLSX instantly — free, no signup required.
Start Converting