Convert XLS to XLSX
Free and instant — your XLS files are processed securely on our servers and deleted right after conversion. Nothing is stored.
How to convert XLS to XLSX
- Step 01
Add your XLS files
Drop them into the box above or click to browse. You can add several files at once.
- Step 02
Conversion starts instantly
Your file is sent to our servers, converted and deleted right away — no sign-up, no queue, no waiting.
- Step 03
Download your XLSX files
Save each file individually or grab them all at once. Done.
Why convert XLS to XLSX?
Converting XLS to XLSX brings an old Excel 97-2003 spreadsheet up to the modern format — smaller, more robust and the default in every current spreadsheet app. The most common reason to convert a .xls file: it just won't open cleanly in newer software.
XLS vs XLSX at a glance
XLS is the legacy Excel format — a binary file superseded by XLSX in 2007, still floating around in old templates and archives. XLSX is the standard spreadsheet format — rows, columns, formulas and charts in a file every version of Excel and most office suites can open and edit.
| Property | XLS | XLSX |
|---|---|---|
| Extension | .xls | .xlsx |
| Full name | Microsoft Excel 97-2003 Spreadsheet | Microsoft Excel Spreadsheet |
| First released | 1987 | 2007 |
| Developed by | Microsoft | Microsoft |
| Compression | Lossless | Lossless |
| Transparency | No | No |
| Animation | No | No |
| Best for | old Excel spreadsheets from Office 97-2003 that newer apps struggle to open | editable spreadsheets, data tables and financial reports compatible with Microsoft Excel |
XLS to XLSX — frequently asked questions
Is this XLS to XLSX converter really free?
Yes — completely free, with no sign-up, no watermarks and no daily limits.
Will formulas and formatting survive the conversion?
Yes — formulas, cell formatting and multiple sheets are preserved. Very old macros specific to the binary format may not carry over.
Is the conversion private?
Your XLS is sent to our servers, converted using LibreOffice, and the result is returned to you. Your file is deleted immediately after conversion and never stored.
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