CSV to XLS for systems that still need Excel 97 to 2003

Some government portals, banking upload screens and older ERP import wizards accept only the .xls extension and reject XLSX outright. If your data starts life as CSV, you need a converter that writes the genuine binary format, not a renamed file that the importer will refuse.

XlsConverter writes a real BIFF8 workbook that Excel 97 and later, and the legacy tools built around it, can read. If your target accepts modern files, CSV to XLSX is the better choice. To upgrade an existing old workbook, see XLS to XLSX.

How to convert CSV to XLS in three steps

1. 1Upload the CSV file.
2. 2Confirm the delimiter, encoding and which columns are text.
3. 3Convert and download the .xls workbook.

Fitting modern CSV data into the limits of the XLS format

XLS holds at most 65,536 rows and 256 columns per sheet, and a cell can hold up to 32,767 characters. A CSV exported from a current system easily exceeds the row limit. We continue the data on Sheet2 and onward with the header repeated, or produce separate files if the importer reads only the first sheet.

Legacy importers are also strict about content. Some reject cells with line breaks, others choke on characters outside their code page. You can strip line breaks inside fields and trim whitespace before the XLS is written. Values longer than the cell limit are flagged in the job report rather than cut off silently.

Numbers in XLS are stored as 64 bit floating point, the same as XLSX, so IDs longer than 15 digits must be stored as text to survive. Dates are written as real Excel dates using the 1900 date system that older tools expect. If the receiving system can take a cleaner format, CSV to XML or CSV to JSON avoid these limits entirely.