XLS to XLSX converter
A free XLS to XLSX converter for Microsoft Excel 97-2003 Workbook files. Browser-based pairs here usually run in this tab, with no file upload.
Drop your XLS files here
or browse your device · paste with Ctrl+V
Accepts .xls files. You can queue several files; each is processed one after another on your own device.
Your files never leave this device — there is no upload and no server to delete them from.
- 01
Add your XLS files
Drop them onto the box above or click to browse. They are read straight from disk — nothing is sent anywhere.
- 02
Check the settings
XLSX is already selected. Open the gear icon on any row if you want to change quality, dimensions or codec before converting.
- 03
Download your XLSX
Press convert and wait for the row to finish. Convert several files and you can take them all as a single ZIP.
XLS
Microsoft Excel 97-2003 WorkbookThe legacy binary Excel workbook, capped at 65,536 rows and 256 columns. Those limits alone are usually reason enough to convert an old XLS to XLSX.
- Developed by
- Microsoft
- Released
- 1987
- Extension
- .xls
- MIME type
- application/vnd.ms-excel
- Compression
- Uncompressed
XLSX
Office Open XML SpreadsheetExcel's modern workbook format, holding multiple sheets, formulas, formatting and charts as zipped XML. The de facto standard for exchanging tabular data in business.
- Developed by
- Microsoft / ECMA
- Released
- 2007
- Extension
- .xlsx, .xlsm
- MIME type
- application/vnd.openxmlformats-officedocument.spreadsheetml.sheet
- Compression
- Lossless
- Specification
- Open
Questions about converting XLS to XLSX
Is this XLS to XLSX converter free?
Yes. Converting XLS to XLSX here is free, with no account, no watermark and no daily quota. The work runs on your own device, so there is no server cost to pass on to you.
Is my XLS file uploaded anywhere?
For browser-based pairs, your file is read locally and converted by SheetJS in this tab. No file payload is uploaded; you may still see analytics and engine downloads in network logs.
Is there a file-size limit for XLS to XLSX?
There is no imposed upload cap when it runs in-browser, but each conversion still depends on your device and browser memory. Large videos are the first practical limit, then memory-heavy documents or images.
Can I convert several XLS files to XLSX at once?
Yes. Drop in several files and each gets its own row; they are processed one after another on your device. You can download them one by one or as one ZIP.
Does XLS to XLSX work on a phone, Mac or Chromebook?
Most modern browsers on Windows, macOS, Linux, ChromeOS, Android and iOS work. Very large videos are often more reliable on desktop or a browser with more memory.
Why do some conversions take longer on first run?
The conversion engine has to download first. Small codec bundles are fast, while ffmpeg is commonly 12–30 MB; later conversions of similar type use the cached engine.
I converted a file and the output is blank or unusable. What should I check?
Start over with default settings, then change one option at a time (quality, bitrate, page size, or codec) to isolate what changed behavior. If it keeps failing, retry with a smaller file and confirm the source format matches the pair.
Convert other formats to XLSX
4 formats can become XLSX here.
Convert XLS to other formats
A XLS file can become any of these.
XLSX to XLS
The reverse conversion
CSV to XLSX
HTML to XLSX
XLS to CSV
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