XLSX to XLS
Convert to the Excel 97-2003 (.xls) format for legacy systems
Drag & drop files here
or browse files
Supports .xlsx / .xls / .csv - outputs Excel 97-2003 (.xls)
About this tool
Legacy finance systems, old ERP installs, import tools that only accept Excel 97-2003 - sooner or later you need a genuine .xls. This tool converts .xlsx (plus .xls/.csv input) into BIFF8 .xls, the standard Excel 97-2003 format with the widest compatibility.
Honest scope: BIFF8 dates to 1997 with a 65,536-row × 256-column ceiling per sheet - oversized files fail with a clear message instead of silent truncation, and modern themes, charts and new functions do not carry over. Conversion runs locally in your browser - nothing is uploaded.
Features
- Accepts .xlsx / .xls / .csv, outputs Excel 97-2003 (.xls)
- Standard BIFF8 output for maximum legacy compatibility
- Explicit errors past 65,536 rows / 256 columns - no silent cuts
- Multi-sheet structure preserved
- Free, unlimited, local conversion
How to use
- Drop or select the .xlsx file
- Click Convert
- Download the .xls file
- Open it in the legacy system or old Office
Frequently asked questions
- What is the difference between xls and xlsx?
- xls is the Excel 97-2003 binary format (BIFF8); xlsx is the Open XML format since 2007. xls wins on legacy compatibility, xlsx on size and features. Keep xlsx for new work and convert only when a system demands xls.
- Does the data change after converting?
- Cell values (text, numbers, dates) carry over as-is; 2007+ features such as new functions, themes and charts do not. Spot-check key data after converting.
- Why does my file fail to convert?
- Most likely the BIFF8 ceiling: 65,536 rows or 256 columns per sheet. The tool reports it clearly rather than truncating - split or trim the sheet first.
- Do I need to upload the file anywhere?
- No. SheetJS converts it inside your browser; the file never leaves your device.