How to convert XLS to XLSX
1. Upload XLS
Select or drag and drop your XLS file into the converter.
2. Choose XLSX
Select XLSX as your output format. You can process multiple files at once.
3. Download
Click convert and download your new XLSX file instantly.
Format Details
XLS
XLS is the legacy binary spreadsheet format used by Microsoft Excel from 1987 through the Office 2003 era, based on Microsoft's proprietary Binary Interchange File Format (BIFF). It stores worksheets, formulas, charts, and macros in a binary structure that requires Microsoft's format specification to parse correctly. XLS remains common in older enterprise systems and when compatibility with legacy versions of Excel is required.
XLSX
XLSX is the default spreadsheet format for Microsoft Excel since Office 2007, built on the Open XML standard and standardized by ISO. It stores worksheets, formulas, charts, pivot tables, and formatting in a compressed ZIP archive of XML files, making it more compact and corruption-resistant than the older XLS format. XLSX is supported by Google Sheets, LibreOffice Calc, Apple Numbers, and virtually every modern data tool.
Frequently Asked Questions
How do I convert XLS to XLSX?
Upload your XLS file on Convertek, select XLSX as the output format, then click Convert. Your XLSX file will be ready to download instantly.
Is the XLS to XLSX converter free?
Yes. Converting XLS to XLSX on Convertek is completely free with no watermarks. Fair upload limits apply (typically 30 MB per file).
Is my file kept after conversion?
No. Files are processed temporarily and not stored permanently. Converted downloads are available only in your browser session.
What is the difference between XLS and XLSX?
XLS and XLSX are different file formats with distinct use cases. Converting between them lets you use your file in software or workflows that require the XLSX format.