Microsoft Excel is one of the most widely used tools when it comes to data analysis, management, and accounting operations. This software allows users to create, edit, and save spreadsheets. However, not everyone has the software installed on their computer or can afford to pay for it. Thankfully, there are ways to open XLS and XLSX files for free.

Here are some of the ways:

1. Google Sheets: Google Sheets is a free, web-based spreadsheet program offered by Google. It allows users to create, edit, and share spreadsheets online. Users can import XLS and XLSX files and convert them into Google Sheets format. To use Google Sheets, all you need is a Google account.

2. OpenOffice Calc: OpenOffice is a free, open-source office suite that includes a spreadsheet program called Calc. This program can open XLS and XLSX files and allows users to create and save spreadsheets in different formats. OpenOffice Calc has features similar to Microsoft Excel, including data analysis tools, charts, and graphs.

3. LibreOffice Calc: LibreOffice is another free, open-source office suite that includes a spreadsheet program called Calc. This program can open XLS and XLSX files and offers features similar to OpenOffice Calc and Microsoft Excel. LibreOffice Calc also includes a comprehensive set of formulas and functions for data analysis.

4. Zoho Sheet: Zoho Sheet is a free, online spreadsheet program that allows users to create, edit, and share spreadsheets. It supports various file formats, including XLS and XLSX. Zoho Sheet offers many features similar to Google Sheets and Microsoft Excel, such as data visualization tools, charts, and graphs.

5. Microsoft Excel Online: Microsoft provides a free, online version of Excel called Excel Online. This program allows users to view, edit, and share Excel spreadsheets online. It supports various file formats, including XLS and XLSX. Excel Online also includes many of the features found in the desktop version of Excel, such as formulas, charts, and PivotTables.