Free online BAK to XLS converter

A legacy business system may require an Excel 97–2003 workbook, or a backup may contain tabular document data that must be edited or shared in Excel. Converting it requires identifying the application that created the backup, opening or restoring its contents, and saving the recovered data as .xls.

What the BAK format is

.bak is a generic backup filename extension, not a standardized document format. Document editors, office applications, and other software may create it as a copy of an earlier file during saving, automatic backup, or manual archiving. The file normally retains the original application's internal structure; the extension only describes its backup role.

The same extension can therefore contain an Excel workbook, delimited text, a word-processing document, or a proprietary project file. Identify the creating application from the surrounding files, filename, folder, documentation, or a file-identification utility before attempting conversion. A BAK file that is not spreadsheet or tabular data cannot be converted directly into an XLS workbook.

What the XLS format is

.xls is Microsoft Excel's binary BIFF workbook format used primarily by Excel 97–2003. It can contain worksheets, cell values, formulas, formatting, charts, and some macro content, and remains useful when a legacy application or recipient does not support .xlsx.

Each worksheet supports a maximum of 65,536 rows and 256 columns. XLS also lacks support for some newer Excel features, so conversion from a modern workbook can remove or alter tables, formulas, formatting rules, charts, links, or macros.

How to convert a BAK file to XLS

1. Copy the BAK file to a working folder and leave the original unchanged. A backup may be the only usable version of the document.
2. Determine what created the file. Check the original document's application, nearby files, backup settings, and file metadata. If available, inspect the file signature; a filename extension is not reliable evidence of the internal format.
3. Try opening the copy in Microsoft Excel or LibreOffice Calc. In Excel, use File → Open → Browse, change the file filter to All files, and select the BAK copy. In Calc, use File → Open. Do not force an import if the program reports that the file is not a workbook.
4. If the application recognizes the internal workbook, use File → Save As and choose Excel 97–2003 Workbook (*.xls). In LibreOffice, select File → Save As and choose Excel 97–2003 (.xls). Give the output a new filename.
5. If the BAK is a renamed copy of an Excel workbook, restore the extension documented by the source application first, such as .xlsx or .xls, then open it and save it as the required .xls. Renaming alone does not perform conversion.
6. If the file contains delimited text, open it in Excel with Data → From Text/CSV, or open it in Calc and configure the delimiter, character encoding, text qualifier, and column types in the import dialog. Then save the imported sheet as .xls.
7. If Excel and Calc cannot open the file, use the application that created the backup to restore or repair it, then export its tabular content to XLS. Proprietary document backups may need to be restored to the original document before their data can be exported.

The free converter on 101convert.com can be used without installing software when it accepts the particular BAK content and provides XLS output. A generic BAK file is not guaranteed to be supported because the extension does not identify its internal format.

Quality and compatibility limits

A BAK-to-XLS conversion is often a recovery and export process rather than a direct format conversion. Restoring a document may recover only the state saved in the backup; unsaved changes, damaged sections, application-specific metadata, embedded objects, and unsupported features may be absent.

When saving a newer workbook as XLS, review any compatibility warning and check formulas, displayed values, worksheet names, charts, merged cells, conditional formatting, external links, macros, and print settings. Password-protected, encrypted, corrupted, or partially written backups may require recovery in the source application before export.

For text imports, verify dates, decimal separators, character encoding, null values, long numbers, scientific notation, and leading zeroes. Spreadsheet software may reinterpret identifiers such as product codes or account numbers unless their columns are imported as text.

Compare row and column counts and several important values with the source or original document. If a worksheet exceeds the XLS limit of 65,536 rows or 256 columns, split the data across sheets or files, or use .xlsx if the receiving software supports it.