Free online WK4 to XLSX converter

Current Microsoft Excel releases may not open an old .wk4 workbook reliably, while business systems and recipients commonly expect .xlsx. Converting the file makes its worksheet data usable in current spreadsheet software and easier to share or archive.

What the WK4 format is

.wk4 is a binary worksheet format associated with Lotus 1-2-3 for Windows, especially version 4-era releases. It can contain cell values, formulas, formatting, multiple worksheets, charts, ranges, and other workbook structures. WK4 files are found mainly in legacy accounting, inventory, engineering, administrative, and personal archives.

What the XLSX format is

.xlsx is Microsoft Excel’s ZIP-based Office Open XML workbook format, introduced with Excel 2007. It supports multiple worksheets, formulas, tables, charts, styles, and current spreadsheet features, and is supported by Excel, LibreOffice Calc, Apple Numbers, Google Sheets, and many document systems. Unlike .xlsm, an XLSX file does not provide a format for storing working VBA macros.

How to convert WK4 to XLSX

LibreOffice Calc is the most useful desktop option to test first because it is free, works offline, and includes import filters for some Lotus 1-2-3 worksheet formats.

1. Make a copy of the original .wk4 file and keep the source unchanged.
2. Install a current desktop version of LibreOffice and open Calc.
3. Select File → Open, choose the copied WK4 file, and accept the Lotus 1-2-3 import settings if Calc displays them. If the file is not shown, change the file filter to All files.
4. Inspect every imported worksheet. Check formulas, totals, dates, decimal values, number formats, column widths, hidden rows or columns, named ranges, charts, and print settings.
5. Select File → Save As, choose Excel 2007–365 (*.xlsx), and save to a new filename such as converted.xlsx.
6. If Calc warns that some content cannot be saved in the selected format, review the warning before confirming the XLSX format rather than retaining ODF.

Open the resulting file in Microsoft Excel or another XLSX-compatible application and compare important calculations with the original before replacing the WK4 copy. LibreOffice’s command-line conversion can be used for a tested batch workflow, but the installed version must have a working WK4 import filter; test one file manually before processing a collection.

If Calc cannot read the file, a compatible legacy Lotus 1-2-3 installation may provide a more accurate import. Some other spreadsheet programs may also support WK4, but support varies by product and version, so test a copy and verify the program’s documented import filters. If the only available export is CSV, convert that single worksheet to XLSX afterward; CSV will not retain formulas, formatting, charts, multiple worksheets, or most workbook metadata.

For a conversion without installing software, use the converter on 101convert.com: upload the .wk4 file, select .xlsx as the output, start the conversion, and download the result. Do not upload confidential or regulated workbooks unless the service’s data-handling terms are acceptable for the file.

Quality and compatibility limits

Basic cell values and ordinary formulas generally transfer more reliably than Lotus-specific functions, macros, embedded objects, charts, print settings, named ranges, borders, and unusual formatting. Lotus 1-2-3 macros and commands do not become Excel VBA macros when the workbook is saved as XLSX. Unsupported formulas may be changed to values, produce errors, or require manual rewriting.

Check dates, currency values, decimal separators, and text encoding because regional settings and legacy storage conventions can alter their interpretation. Confirm that all worksheets, sheet references, formulas, hidden content, and key totals survived the conversion. For financial, operational, or regulatory files, compare the result with the original Lotus 1-2-3 display, a trusted report, or an independent calculation.

A damaged or password-protected WK4 file may need to be opened or repaired in a compatible legacy application before conversion. Keep the original WK4 file as an untouched backup, and do not treat a successful file conversion as proof that every workbook feature was preserved.