Convert XLS to XLSX and keep formulas and formatting

XLS files open in compatibility mode, are larger than needed, cannot exceed 65,536 rows and are blocked by some email filters and document systems. Converting them to XLSX gives a smaller, safer file with modern limits, and it is the first step of most spreadsheet archive cleanups.

XlsConverter keeps formulas and styles where the XLSX format supports them, which is nearly everywhere. To go the other direction for a legacy tool, use XLSX to XLS. To move the upgraded file into Google Workspace, see XLS to Google Sheets.

How to convert XLS to XLSX in three steps

1. 1Upload one XLS file or a batch.
2. 2Choose to keep formulas or replace them with values.
3. 3Convert and download the XLSX files.

What carries over from BIFF8 to Open XML and what does not

XLS stores everything in one binary stream called BIFF8, while XLSX is a ZIP of XML parts. The data, formulas, styles, merged cells, named ranges, freeze panes and column widths all have direct equivalents and are converted one to one. The new file is typically much smaller because the XML parts are compressed.

Some things do not map perfectly. VBA macros cannot live in an .xlsx file at all (that would need .xlsm), so macro code is not carried over and the report says so. The old palette of 56 colors is translated to exact RGB values, and charts made in very old Excel versions may look slightly different. Formulas that referenced cells beyond row 65,536 never existed in XLS, so nothing breaks there.

Once in XLSX, the sheet can grow to 1,048,576 rows and 16,384 columns, which means data that was split across Sheet1 to Sheet4 can be joined into one sheet with the merge option. If the next step is data processing rather than editing, XLS to CSV or XLS to JSON may be more direct.