Free online EXCEL to XLS converter

An older reporting system, accounting application, or hardware device may accept only .xls files, while current spreadsheet software normally creates .xlsx workbooks. Saving a workbook as XLS also provides compatibility with users running Excel 2003 or other legacy spreadsheet programs.

What the Excel format is

“Excel” usually refers to a Microsoft Excel workbook, most commonly a file with the .xlsx extension. XLSX was introduced with Excel 2007 and uses Office Open XML: a ZIP-compressed package of XML files. Workbooks can contain worksheets, formulas, formatting, charts, tables, images, named ranges, and other spreadsheet features.

Microsoft Excel, LibreOffice Calc, Apple Numbers, and compatible business applications create or edit XLSX files. The format is common for reports, exported business data, financial models, and shared spreadsheets. Macro-enabled workbooks normally use .xlsm rather than .xlsx.

What the XLS format is

.xls is Excel’s older binary workbook format, based on the BIFF format and used by Microsoft Excel through Excel 2003. It can store worksheets, formulas, charts, formatting, and VBA macros, but it supports fewer modern features and has lower worksheet limits than XLSX.

XLS is useful when a legacy application requires the binary format or cannot open XLSX. It is not automatically smaller: XLS uses a binary structure, whereas XLSX uses ZIP compression. Converting only for file-size reduction is therefore unreliable.

How to convert an Excel workbook to XLS

Using Microsoft Excel

1. Open the source workbook in Excel and check formulas, charts, links, hidden sheets, and macros.
2. Choose File → Save As or File → Save a Copy.
3. Set the file type to Excel 97-2003 Workbook (*.xls).
4. Choose a destination and enter a filename. Keep the .xls extension if Excel does not add it automatically.
5. Select Save. If Excel displays a compatibility warning, review the listed features and choose Use Excel 97-2003 Format.
6. Close and reopen the generated .xls file before sending it or importing it into another system.

Using LibreOffice Calc

1. Open the workbook in LibreOffice Calc.
2. Choose File → Save As.
3. Select Excel 97-2003 (*.xls) as the file type and enable Automatic file name extension if needed.
4. Select Save, then confirm Use Excel 97-2003 Format when prompted.
5. Reopen the saved file in Calc or the target application and inspect the results.

Using 101convert.com

You can convert the file on 101convert.com for free without installing software: upload the workbook, select XLS as the output format, start the conversion, and download the result. Do not upload confidential or regulated spreadsheets unless the service’s current privacy and retention terms are acceptable for that data.

Compatibility limits and quality checks

Each XLS worksheet supports a maximum of 65,536 rows and 256 columns. Data outside those limits cannot be represented in the legacy format and may be lost during conversion. Excel may also remove or change features that XLS does not support, including some table functionality, conditional-formatting rules, newer chart types, slicers, structured references, threaded comments, and modern data-model functions.

VBA macros can be stored in XLS, but preservation depends on the source file and the application used for saving. Check macro security settings and test the converted workbook in the target environment; changing the extension does not preserve or convert macro code by itself.

After conversion, verify formulas, dates, number formats, merged cells, print areas, page breaks, charts, hidden sheets, named ranges, and external links. Renaming .xlsx to .xls is not a conversion and generally produces an invalid or unreadable file.