Excel to Excel Converter Online

Need to convert XLS to XLSX and update your legacy Excel files to the modern format? This tool upgrades old binary Excel files to the current standard format, making them fully compatible with all modern versions of Excel, Google Sheets, and LibreOffice Calc.

What Is the Difference Between XLS and XLSX?

XLS is the binary format used by Microsoft Excel through version 2003. It stores spreadsheet data in a proprietary binary structure. XLSX is the format introduced with Excel 2007 as part of the Office Open XML standard. It stores data as a compressed collection of XML files, which is an open, well-documented, and widely supported format.

The practical differences matter for everyday use. XLSX files are smaller than equivalent XLS files because of compression. XLSX opens more reliably in non-Microsoft applications because it uses an open standard. XLSX supports larger spreadsheets with more rows and columns than XLS. Most importantly, all current versions of Excel, Google Sheets, LibreOffice, and other spreadsheet applications treat XLSX as their native format and offer the best compatibility and full feature support for it.

Why Convert XLS to XLSX?

Software compatibility is the most common reason. If you use Excel 2007 or later, Google Sheets, or LibreOffice, converting your XLS files to XLSX means working in the native format of those applications. Some advanced Excel features introduced after 2007 are only available in XLSX format and cannot be saved to XLS. Converting enables access to the full modern Excel feature set.

File size reduction is a practical benefit. XLSX compression typically produces files 25 to 50 percent smaller than equivalent XLS files. For large spreadsheets with many rows or embedded content, this size difference is significant for storage and email attachment purposes.

Organizational standardization is another common reason. Teams that have mixed libraries of XLS and XLSX files often convert everything to XLSX for consistency. A single format across all files simplifies backup, version control, and sharing workflows.

Future compatibility is an important consideration. Microsoft and other developers continue to invest primarily in XLSX support. XLS is a legacy format that will receive progressively less attention over time. Converting these archives now ensures the files remain fully functional in future software versions.

What Is Preserved During Conversion

All cell data transfers to the XLSX output including text, numbers, dates, and calculated formula values. Basic formatting such as bold text, font sizes, and number formats is preserved where XLSX equivalents exist. Multiple sheets from the XLS file are included in the XLSX output. Charts and images embedded in the XLS file transfer to the XLSX where compatible.

Complex macros written in the old XLS macro format may not transfer to XLSX. If your XLS file contains macros, they should be reviewed and recreated in the Excel macro format after conversion.

How to Convert XLS to XLSX Online

Upload your XLS file by clicking the upload button or dragging it into the upload area. The converter reads the legacy binary structure and writes all content into a properly formatted XLSX file. Download the XLSX file once processing is complete. Open it in Excel, Google Sheets, or LibreOffice and verify the content before using it as your primary file. Uploaded files are deleted from the server automatically after download.