XLS to XLSX Converter

The old .xls format (Excel 97–2003) is limited to 65,536 rows and is blocked or opened read-only by some current software and mail filters. This converter rewrites .xls workbooks as .xlsx inside your browser, several at a time. Values, formulas, number and date formats, merged cells, column widths, row heights, sheet names and hidden sheets carry over. Each new file is read back and checked cell by cell before you download it. Your workbooks are not uploaded anywhere.

How to use this tool

1. Choose one or more .xls files.
2. Wait for each file to be converted and checked; the table shows sheets, cells and formulas.
3. Download the .xlsx files, or all of them as one ZIP.
4. Open a converted file and reapply fonts, colours or borders if you need them.

Formula

.xls (BIFF8 records in an OLE compound file) → workbook model → .xlsx (Office Open XML: zipped XML parts)

The workbook is parsed with the open-source SheetJS library and written again as Office Open XML. Formulas are kept as formulas together with their last calculated values, so Excel shows the same numbers before recalculating. Cell styles are not written by this library, so fonts, fill colours, borders and conditional formatting fall back to Excel's defaults. Charts, images, comments, data validation and VBA macros are also not carried over, which the result notes repeat. Encrypted .xls files must be unlocked in Excel first.

Example

A 1.2 MB budget2009.xls with three sheets, 4,812 filled cells and 310 formulas becomes budget2009.xlsx with the same three sheets, 4,812 cells and 310 formulas. The .xlsx is ZIP-compressed, so it is usually smaller than the .xls. Every value matches on reading back, and the "Read-back check" shows OK.