Why Convert XLS to XLSX?

The XLS format is based on the older Binary Interchange File Format (BIFF), which has a maximum row limit of 65,536 rows and 256 columns. In contrast, XLSX (based on Office Open XML) supports up to 1,048,576 rows and 16,384 columns. Additionally, XLSX files are typically 30-50% smaller due to ZIP compression, and they offer better data recovery options, enhanced security, and native support for features like conditional formatting, PivotTables, and macros (with proper handling).

Method 1: Convert XLS to XLSX Using Microsoft Excel (Manual)

The simplest way is to open the XLS file in Excel (version 2007 or later) and use the 'Save As' or 'Export' feature:

  1. Open the XLS file in Excel.
  2. Click on File > Save As (or File > Export > Change File Type).
  3. Choose Excel Workbook (*.xlsx) from the drop-down menu.
  4. Click Save.

This method works perfectly for single files, but if you have many, you'll need a batch conversion tool.

Method 2: Batch Convert XLS to XLSX Using Online Tools

For multiple files or when you don't have Excel installed, online converters are a great free option. AXZTools.com offers a dedicated XLS to XLSX converter that supports batch uploads, high conversion speed, and maintains formatting. Just drag and drop your XLS files, click convert, and download the XLSX versions. No registration required.

Method 3: Convert Without Excel Using Command Line or Scripts

Advanced users can use Python libraries like openpyxl or pandas to automate conversion. A simple script using pandas:

import pandas as pd
df = pd.read_excel('input.xls')
df.to_excel('output.xlsx', index=False)

This requires installing pandas and xlrd (for old XLS) and openpyxl (for XLSX).

What About Macros and VBA?

If your XLS file contains macros, converting it to XLSX will remove them because the XLSX format does not support macros. To preserve macros, save as a macro-enabled workbook (.xlsm) instead. Most online tools also offer XLSM conversion if needed.

Common Questions About XLS to XLSX Conversion

Will I lose any data or formatting?

Generally, no. The conversion process preserves cell content, formulas, formatting, and charts. However, some very old features (like Excel 5.0 dialog sheets) may not be supported in XLSX. Always verify a sample file after conversion.

Can I convert XLSX back to XLS?

Yes, but you may lose features not supported in the older format (e.g., more than 65k rows). Use the 'Save As' -> 'Excel 97-2003 Workbook (*.xls)' option in Excel.

Is it safe to use online converters?

Choose reputable services that use HTTPS and process files server-side without storing them permanently. AXZTools.com automatically deletes your files within 1 hour for privacy.

Tips for a Smooth Conversion

  • Always back up original XLS files before bulk conversion.
  • If your workbook contains multiple sheets, most tools handle them correctly.
  • For large files (over 100 MB), consider using desktop software for faster processing.

Switching to XLSX is one of the best upgrades you can make for your data management. Whether you use Excel, Google Sheets, or LibreOffice, the modern format ensures better compatibility and performance. Start converting your XLS files today with our free online tool at AXZTools XLS to XLSX Converter.