Convert XLS to XLSX
Send us an Excel 97-2003 workbook and get back an .xlsx package written by LibreOffice on our servers, with the sheet data rewritten into the modern Office Open XML package. One thing to know up front: XLSX cannot store VBA, so any macros in the old file are left behind.
Download Started!
How would you rate your experience with MiConvert?
Why convert XLS to XLSX
XLS is Excel's old binary workbook format, the one Excel 97 through 2003 wrote by default. The data sits in a proprietary record stream rather than in files you can read, which is why so much modern software refuses it: web spreadsheet editors ask for .xlsx on import, many Python readers now expect the zipped XML that openpyxl understands, and plenty of accounting, ERP and HR upload forms list .xlsx as the only accepted spreadsheet type. The numbers in the file are fine; the container is the problem.
This page runs the pair through headless LibreOffice 7.4 on our servers, using its Calc Office Open XML export filter. Microsoft Excel is not involved at any point, and nothing is installed on your machine. Renaming a .xls to .xlsx by hand does not work, because the bytes inside are still the old binary record stream.
LibreOffice parses the binary workbook and writes a fresh Office Open XML package through its Calc export filter, so sheet data and cell values are carried into the new file. We have not verified how every legacy feature survives this pair, so open the result and compare: formulas, number formats, charts, pivot tables and form controls are rebuilt from LibreOffice's reading of the file rather than copied record for record, and they can shift. VBA macros cannot travel at all, because the .xlsx format has no place to put them, and we do not output .xlsm.
The people who need this are usually clearing out shared drives full of .xls attachments, feeding old reports into a tool that only accepts .xlsx, or working on a machine with no Excel license. It is also the quickest answer to the common request to change .xls to .xlsx without opening the file in a spreadsheet application first.
How to convert an XLS file to XLSX
- If the workbook has a password on it, open it in Excel or LibreOffice Calc and save an unprotected copy first. Legacy .xls encryption is not detected by our checks, so a protected file comes back only as "could not be opened" rather than with a password prompt.
- Confirm the extension matches the contents. Files that are really CSV, HTML or an older database export but carry a .xls name are a frequent cause of failure, because LibreOffice reads the bytes, not the name.
- Drop the .xls onto the upload box, or pick several at once. Guests can send files up to 50 MB and 10 per request; a free account raises the per-file ceiling to 100 MB, Plus to 200 MB and Pro to 1 GB.
- Start the conversion. The file is uploaded over HTTPS and converted on our servers; at the typical size for this pair, around 150 KB, results have been coming back in about a second.
- Download the .xlsx. The link stays valid for roughly four hours, so grab it in the same session if you can.
- Open the result and check anything that is not plain cells, especially formulas, charts and pivot tables on the oldest workbooks.
What this converter does
- Reads the legacy BIFF binary format with LibreOffice 7.4 in headless mode and writes the result through its Calc Office Open XML export filter.
- Re-saves the workbook rather than renaming it: LibreOffice builds a new document model from the binary file and writes a genuine .xlsx package, which is why a hand-renamed .xls still errors and a converted one opens.
- Needs no Excel installation, no plugin and no account, and works the same from Windows, macOS, Linux, ChromeOS or a phone browser.
- Takes several workbooks in one request, up to 10 files for guests and free accounts, 25 on Plus and 50 on Pro. Each converted file is downloaded on its own; there is no combined ZIP.
- Returns specific messages instead of a blank failure for unreadable or truncated uploads and for unsupported pairs. Legacy .xls encryption is the exception: it is not detected, so a protected workbook comes back only as "this document could not be opened".
- Handles the other common targets for the same file too: .xls can also be converted to PDF, CSV or HTML here.
Video Tutorial
Watch this step-by-step tutorial to learn how to convert XLS files to XLSX format online for free using MiConvert.com. No software installation required.
XLS to XLSX questions
Will my formulas and formatting survive the conversion?
The sheet data and cell values are rewritten through the LibreOffice Calc Office Open XML export filter. We do not claim an identical copy, and we have not verified every legacy feature for this pair: formulas, number formats, charts, pivot tables, form controls and very old Excel-specific features are re-created from LibreOffice's reading of the file, so check those sheets after you download.
Can I convert XLS to XLSX without opening the file in Excel?
Yes, that is exactly what happens here. You never open the workbook; you upload it, our server converts it and you download the .xlsx. No copy of Excel is needed on your side, which is the usual reason people look for this rather than using File, Save As.
What happens to VBA macros in the old .xls?
They are gone from the output. The .xlsx format is defined without macro storage, so no converter can put them there, and we do not produce .xlsm files (that extension is also refused at upload). Keep the original .xls as your macro copy, or open it in Excel on a desktop and save it as .xlsm yourself.
Can I convert a whole folder of XLS files automatically?
You can upload a batch in one request, within the file counts above, and each file comes back as its own .xlsx download. There is no watch folder and no scheduled job here, so for a recurring task on your own machine use LibreOffice's command line (soffice --headless --convert-to xlsx) or a Python script instead.
Why did my conversion fail?
Three causes cover almost everything. The file is password-protected, in which case save an unprotected copy first. The file is not really an .xls, so re-save it in its actual application under the right extension. Or the workbook is damaged or did not finish uploading, which shows as "this document could not be opened" and is usually fixed by opening and re-saving it in Excel or Calc before trying again.
Is XLS the same thing as XLSX?
No. XLS is the binary workbook Excel used through 2003, while XLSX, from Excel 2007 onward, is a ZIP archive of XML parts, which is why it compresses better and can be read by software that was never written for Microsoft's old binary record format.
How large a file can I upload?
50 MB without an account, 100 MB with a free one, 200 MB on Plus and 1 GB on Pro. Rate limits apply per IP as well: 10 conversion jobs an hour for guests and free accounts, 50 an hour on the paid plans. Spreadsheets in this pair are usually well under a megabyte, so the ceiling rarely matters.
What happens to my spreadsheet after conversion?
It is uploaded over HTTPS and converted on our servers, not in your browser. The uploaded .xls is deleted as soon as the job finishes, and the converted .xlsx stays downloadable for about four hours through a random, unguessable link before it is deleted automatically. File names, sizes and outcomes are recorded in our logs, and signed-in users see the conversion in their history.