Convert XLS to XLSX Online
Limited to 65,536 rows and 256 columns — a fraction of the 1M+ rows in modern XLSX files. Converting to XLSX gives you a key advantage: full-featured spreadsheet with 1,048,576 rows, formulas, pivot tables, charts, macros (xlsm), and conditional formatting. XLSX is best for business data analysis with formulas, pivot tables, charts, and conditional formatting.
Why Convert XLS to XLSX?
Limited to 65,536 rows and 256 columns — a fraction of the 1M+ rows in modern XLSX files — converting to XLSX overcomes this by providing full-featured spreadsheet with 1,048,576 rows, formulas, pivot tables, charts, macros (xlsm), and conditional formatting
XLSX is the right choice when you need to: building financial models and business reports with complex formulas
Gain broader compatibility — XLSX works with Microsoft Excel, Google Sheets, LibreOffice Calc, Apple Numbers, WPS Spreadsheets, OnlyOffice
Your XLS files were created for maintaining backward compatibility with enterprises still using office 2003, but now you need a format suited to different workflows
XLS vs XLSX — Format Comparison
Microsoft Excel Binary Spreadsheet (.xls)
Microsoft Excel Open XML Spreadsheet (.xlsx)
How to Convert XLS to XLSX
Upload your XLS file
Drag your .xls file onto the upload area or click to browse. We accept XLS files up to 100 MB.
Choose XLSX as output format
Select .xlsx (Microsoft Excel Open XML Spreadsheet) from the format list. Configure any format-specific settings to match your requirements.
Convert and download
Click Convert and wait for processing. Your XLSX file will be ready to download in seconds. The result is optimized for business data analysis with formulas, pivot tables, charts, and conditional formatting.
Frequently Asked Questions
Is the XLS to XLSX conversion lossless?
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When both formats support lossless data, the conversion preserves all content. Complete spreadsheet with formatting, formulas, charts, pivot tables, data validation, and multi-sheet workbooks.
How large will my XLSX file be compared to the original XLS?
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XLS files are typically 50 KB – 30 MB, while XLSX files are typically 50 KB – 50 MB. The actual size depends on content complexity and any quality settings you choose.
What software can open the converted XLSX file?
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XLSX is compatible with: Microsoft Excel, Google Sheets, LibreOffice Calc, Apple Numbers, WPS Spreadsheets, OnlyOffice.
What is the maximum file size I can convert?
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PureConverter accepts XLS files up to 100 MB. Your files are processed securely and deleted from our servers after conversion.
What's the difference between XLS and XLSX?
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XLS (Microsoft Excel Binary Spreadsheet) is best for opening legacy excel 97-2003 spreadsheets from older business systems and archives. XLSX (Microsoft Excel Open XML Spreadsheet) is best for business data analysis with formulas, pivot tables, charts, and conditional formatting. Key tradeoff: XLS's advantage is binary format that loads faster than xlsx for very large files, with backward compatibility to excel 97, while XLSX's advantage is full-featured spreadsheet with 1,048,576 rows, formulas, pivot tables, charts, macros (xlsm), and conditional formatting.
Pro Tips for XLS to XLSX Conversion
Review the output XLSX file to ensure all formatting and content transferred correctly from your XLS source
Keep a backup of your original XLS file — while our conversion is reliable, having the source is always recommended
XLSX works especially well for: creating project budgets and timelines with charts and data validation
Did you know? An XLSX file is a ZIP archive of XML files — the cell data, formulas, and styles are stored in separate XML files that reference each other through relationships.
Ready to Convert?
Upload your XLS file above and get your XLSX in seconds. Free, fast, and secure.