Convert XLS to XLSX

Convert XLS to XLSX instantly in your browser. Your spreadsheet data is processed on your device and never uploaded.

Your file never leaves your device.

How to convert XLS to XLSX

XLSX opens natively in Excel, Google Sheets, Numbers and LibreOffice with typed columns, widths and multiple sheets. This tool reads the XLS with SheetJS, a proven spreadsheet engine, directly in your browser and writes a correct XLSX file with the right encoding, escaping and structure. There are no rows to copy by hand and no data leaves your computer.

Step 1: Choose your XLS file
Drag and drop a .xls file onto the converter or click to browse. It works on desktop, tablet and phone.
Step 2: Automatic conversion
Rows and columns are read and written as XLSX in a fraction of a second.
Step 3: Download the XLSX
Save each result individually, or download everything as a single ZIP when you convert several files.

Good to know

All sheets, values, formulas, number formats and column widths are carried over. Charts, pivot tables and macros are not converted.

Why use this XLS to XLSX converter?

XLSX opens natively in Excel, Google Sheets, Numbers and LibreOffice with typed columns, widths and multiple sheets.
Handles large files with thousands of rows.
Correct quoting and UTF-8 encoding.
100% local: spreadsheets often contain personal or financial data, and here it never leaves your device.

Is it free?

Yes. Converting XLS to XLSX is free, with no watermark, signup or email required. Local conversions have no artificial file-size or daily cap; the practical limit is your device.

Is my file uploaded?

The XLS file is processed entirely in your browser. It is never uploaded, never stored and never seen by anyone, so this is safe for confidential files.

About the formats

What is XLS?

XLS is the binary workbook format used by Microsoft Excel up to version 2003. It stores sheets, formulas, formatting, charts and macros in a single file. Each sheet is limited to 65,536 rows and 256 columns, a limit that the XML-based XLSX, the default since Excel 2007, raised considerably.

Use XLS only when an old version of Excel or a legacy system requires it. For new work, XLSX handles far larger sheets and is less prone to corruption, and CSV is the simpler choice when you only need to move raw data.

XLS (Excel 97-2003 workbook)

What is XLSX?

XLSX (Excel Open XML) is the standard spreadsheet format from Microsoft Excel, also supported by Google Sheets and LibreOffice Calc. Data is organised into cells and sheets, with support for formulas, functions, charts and formatting. Because the file is a ZIP container of XML, its content stays readable and easy to process.

Use XLSX for tabular data that needs structure and calculation, budgets, inventories, lists and anything with formulas or multiple sheets. When you only need the raw data, you can export a single sheet to CSV or JSON here.

Excel Spreadsheet (XLSX)

Frequently Asked Questions

Is XLS to XLSX conversion free?

Yes. It is free, with no watermark, signup or email required. Local conversions have no artificial file-size or daily cap; the practical limit is your device.

What happens to formulas when converting XLS to XLSX?

Formulas are preserved together with their last calculated values.

Is it safe to convert xls to xlsx here?

Yes. The work happens on your own device with WebAssembly and browser APIs, so the file is not uploaded at all. You can even disconnect from the internet once the page has loaded.

Do I need to install anything?

No. Everything runs in a modern browser (Chrome, Edge, Firefox or Safari) on Windows, macOS, Linux, Android and iOS. There is no app, plugin or account.

Can I convert XLSX back to XLS?

Yes, there is a dedicated XLSX to XLS converter linked in the related tools below. Keep in mind that information dropped in one direction cannot always be restored in the other.

Need the opposite? Convert XLSX to XLS

ExcelProcessed locally