XLSX to XLS Converter

AUTO-DELETE/Files are processed on our server and deleted as soon as conversion finishes.

or drop your images here

How to Convert XLSX to XLS Online

XLSX to XLS: what changes in the file

This tool takes a XLSX file, converts it with LibreOffice running on our servers and returns a XLS file.

Saving back to the old binary XLS format: features added after Office 2003 (new chart types, content controls, some effects) may be simplified or dropped.

How XLSX and XLS differ

Property	XLSX	XLS
Full name	Office Open XML Workbook	Excel 97–2003 Workbook (binary)
Introduced	Microsoft, 2007 (ISO/IEC 29500)	Microsoft, 1997
Data type	laid-out document	laid-out document
Strengths	current Excel format; 1,048,576 rows × 16,384 columns per sheet	opens in every version of Excel
Limitations	Excel 2003 and older need a compatibility pack	limit of 65,536 rows × 256 columns per sheet

Measured with a sample file

On September 25, 2026 we ran the tool on our production server with a sample file: a 13-row spreadsheet with a formula (XLSX), 5 KB.

Result: 5 KB → 6 KB, processed in 3.7 s. Output: a valid XLS file (file signature checked).

Real sizes depend on document length, embedded images and fonts; the figures only show the order of change.

Before you convert

The server has DejaVu and Liberation fonts only. Times New Roman, Arial and Courier New keep their layout (Liberation matches their metrics); other fonts such as Calibri or Cambria are substituted, so line breaks and page count can change.
XLS holds at most 65,536 rows × 256 columns per sheet; anything beyond that is cut.
Up to 100 MB per file; a conversion that runs longer than 2 minutes is cancelled.
The file is sent to our server for conversion and deleted as soon as processing ends, including when it fails.

Frequently asked questions

Why convert XLSX back to XLS?

When the recipient only has Office 2003 or older, or an old system only accepts XLS. If it is not required, keep the XLSX.

Will a large spreadsheet be cut?

It can be. XLS holds at most 65,536 rows × 256 columns per sheet; anything beyond that is not kept.

Why did the page count or line breaks change?

The document uses a font the server does not have (only DejaVu and Liberation are installed), so a similar font is substituted. Times New Roman, Arial and Courier New are not affected.

How does the file size change from XLSX to XLS?

With our sample file: 5 KB → 6 KB. Your file may differ depending on its content.