How to convert XLS to XLSX
- 1. Add your XLS file
Drag a XLS file onto the box above, or click to browse. - 2. Choose XLSX
XLSX is already selected as the output — just confirm. - 3. Convert & download
Hit Convert and your new file is ready to save in a second.
XLS and XLSX explained
XLS (Legacy Excel Spreadsheet): The older Microsoft Excel spreadsheet format.
XLSX (Excel Spreadsheet): The modern Microsoft Excel spreadsheet format.
Frequently asked questions
Is it free to convert XLS to XLSX?
Yes. Converting XLS to XLSX on SwiftConvert is completely free, with no sign-up, no watermark and no limits.
Are my files uploaded to a server?
No. The conversion runs entirely in your browser, so your files never leave your device — nothing is uploaded, which keeps your data private.
Will I lose quality converting XLS to XLSX?
The conversion keeps as much quality as the XLSX format allows.
Does it work on Windows, Mac, iPhone and Android?
Yes. It runs in any modern browser on any device — there is nothing to install to convert XLS to XLSX.