Convert Excel 97–2003 (XLS) to Excel (XLSX)
Free online converter for Excel 97–2003 (XLS) files. Office Open XML workbook. Nothing to install, no watermark, and every file is deleted automatically.
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Upload a Excel 97–2003 (XLS) file to convert it to Excel (XLSX). Up to 3 files at once, 100 MB each.
Free · up to 3 files · 100 MB each · files deleted automatically after 1 hour.
About XLS and XLSX
Excel 97–2003 (XLS) .xls
Excel's pre-2007 binary workbook. Capped at 65,536 rows, which is the limit people usually hit before deciding to convert.
Good for
- Opens in very old versions of Excel
- Still emitted by some legacy systems
Trade-offs
- Hard limit of 65,536 rows and 256 columns
- Binary and proprietary
- Superseded for nearly twenty years
application/vnd.ms-excel
Excel (XLSX) .xlsx
Excel's modern workbook format — zipped XML holding sheets, formulas, formatting and charts.
Good for
- Keeps live formulas, not just their results
- Multiple sheets, charts and conditional formatting
- The default in nearly every business
Trade-offs
- Formula compatibility varies between spreadsheet applications
- Heavier than CSV for plain tabular data
application/vnd.openxmlformats-officedocument.spreadsheetml.sheet
XLS and XLSX side by side
| XLS | XLSX | |
|---|---|---|
| Compression | Binary | Zipped XML |
| Animation | No | No |
| Typically used for | Legacy spreadsheets and older exports | Spreadsheets, financial models, reports |
What changes when you convert XLS to XLSX
Rendered by LibreOffice
The conversion runs through headless LibreOffice — the same engine behind the desktop suite, not a lookalike parser. It handles ordinary documents faithfully. Where it can drift is on the elaborate: a document leaning on fonts the server does not have will have them substituted, and the substitute rarely occupies exactly the same width, so line and page breaks can move. Heavily designed layouts are worth checking against the original.
XLS is the pre-2007 binary format
Microsoft replaced XLS with its XML-based successor in Office 2007, and support has been quietly eroding since — recent versions of Office block these files by default on security grounds, because the old binary format can carry macros in ways that are hard to inspect. Converting is usually the right move for anything you intend to keep. Macros are not carried across.
Two suites, two ideas of the same document
XLS and XLSX are the native formats of different office suites, and they do not model documents identically. The text, structure and ordinary formatting come across cleanly. The margins are where care is needed: macros do not transfer, tracked changes and comments can be flattened, and features with no counterpart on the other side are approximated. Read the result before sending it on.
There is a ceiling on rows
A spreadsheet is not a database: the format tops out at 1,048,576 rows and 16,384 columns, and a file approaching either becomes painful to open long before it reaches them. CSV and JSON have no such limit. If your data runs to millions of rows, converting it into a workbook is usually the wrong move — keep it as text and query it with something built for the volume.
Formulas arrive as their results
What is read is the value each cell had last time the workbook was calculated, not the formula that produced it. That is almost always what you want from an export. It does mean the output is a snapshot: nothing in it recalculates, and a workbook saved without being recalculated will export whatever stale values it was holding.