Convert legacy XLS files to modern XLSX format for compatibility with newer Excel versions and Microsoft 365
Accepted formats: .xls
Size up to 100MB
Files deleted automatically
Secure upload (SSL)
Convert your Excel files in 3 simple steps. It's fast, secure, and free!
Drag & drop your .xls file or click to browse. Max size 100 MB
Click on 'Convert' and wait for the conversion to complete.
The converted file will be automatically downloaded in your browser
We convert files using LibreOffice, a trusted open-source office suite. This makes the result consistent and reliable.
Your data stays in place, and we preserve formatting such as cell styles, colors, borders, number formats, formulas, charts, images, and shapes.
No installation and no account required. The tool is completely free and designed to produce stable, repeatable results - with support for files up to 100MB.
A simple overview of the features and benefits of the formats
XLS Format is the classic Microsoft Excel spreadsheet file (versions 97-2003). Data is stored in numbered cells forming rows and columns. It supports static data, complex mathematical formulas, chart-building, and macros (Visual Basic). XLS is widely compatible with most spreadsheet software.
XLSX Format is the modern Microsoft Excel spreadsheet standard used since 2007. Based on the Office Open XML format, it uses ZIP compression to make file sizes much smaller than XLS. It efficiently stores plain text, complex formulas, and graphics in cells, but it does not support macros (for macros, the usual format is XLSM).
The XLS to XLSX converter transforms legacy Excel files into the modern XML-based format introduced in Excel 2007. XLSX uses ZIP compression for smaller file sizes (up to 75% smaller), better data recovery, and improved security. This conversion unlocks newer Excel features like sparklines, slicers, and enhanced charts while maintaining compatibility with Microsoft 365 and cloud platforms. Our tool uses LibreOffice technology to ensure accurate conversion of cell formatting, formulas, charts, and multi-sheet workbooks. Simply upload your legacy XLS file, and download your modern XLSX version in seconds.
Today's tip: XLSX files use ZIP compression, making them up to 75% smaller than XLS files. They also support larger worksheets (1M+ rows), better data recovery, and improved security. XLSX is the default format for Excel 2007 and later, with full compatibility with Microsoft 365 and cloud platforms like OneDrive and SharePoint.
Short answers about XLS to XLSX conversion, formatting, and file security.
Yes. The XLS to XLSX converter is completely free with no hidden fees or subscriptions.
You can upload and convert spreadsheet files up to 100MB.
Yes. We preserve cell formatting, borders, colors, number formats, and formulas during XLS to XLSX conversion.
In most cases, yes. Charts, images, and shapes are transferred to XLSX while keeping the original layout.
XLSX is the modern Excel format with better compression, higher limits, and improved compatibility with Microsoft 365 and cloud platforms.
XLS is the legacy binary format used by Excel 97-2003. XLSX is the newer XML-based format introduced in Excel 2007 with better compression and higher limits.
Yes. All uploads are protected with SSL encryption, and files are automatically deleted after conversion.
No registration required. You can start converting files immediately.
A file of 100 MB will be processed in no more than 10 minutes under average server load.
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