In most cases "xls".
.XLS files are standard Microsoft Excel spreadsheet files. .XLT extension is used for the Excel template files. - Neeraj Sharma
Normally xls is the extension for an Excel spreadsheet document.
Excel 2013 uses a .xlsx extension.
The .xls extension is the extension for Excel files up to version of Excel 2003. A computer will know what versions of Excel it refers to. It also makes it easier for users to identify types of files so they can find their Excel files when they are looking for them. If you did not use the correct extension, both users and the computer will find it harder to find them and the computer may not open them properly.The .xls extension is the extension for Excel files up to version of Excel 2003. A computer will know what versions of Excel it refers to. It also makes it easier for users to identify types of files so they can find their Excel files when they are looking for them. If you did not use the correct extension, both users and the computer will find it harder to find them and the computer may not open them properly.The .xls extension is the extension for Excel files up to version of Excel 2003. A computer will know what versions of Excel it refers to. It also makes it easier for users to identify types of files so they can find their Excel files when they are looking for them. If you did not use the correct extension, both users and the computer will find it harder to find them and the computer may not open them properly.The .xls extension is the extension for Excel files up to version of Excel 2003. A computer will know what versions of Excel it refers to. It also makes it easier for users to identify types of files so they can find their Excel files when they are looking for them. If you did not use the correct extension, both users and the computer will find it harder to find them and the computer may not open them properly.The .xls extension is the extension for Excel files up to version of Excel 2003. A computer will know what versions of Excel it refers to. It also makes it easier for users to identify types of files so they can find their Excel files when they are looking for them. If you did not use the correct extension, both users and the computer will find it harder to find them and the computer may not open them properly.The .xls extension is the extension for Excel files up to version of Excel 2003. A computer will know what versions of Excel it refers to. It also makes it easier for users to identify types of files so they can find their Excel files when they are looking for them. If you did not use the correct extension, both users and the computer will find it harder to find them and the computer may not open them properly.The .xls extension is the extension for Excel files up to version of Excel 2003. A computer will know what versions of Excel it refers to. It also makes it easier for users to identify types of files so they can find their Excel files when they are looking for them. If you did not use the correct extension, both users and the computer will find it harder to find them and the computer may not open them properly.The .xls extension is the extension for Excel files up to version of Excel 2003. A computer will know what versions of Excel it refers to. It also makes it easier for users to identify types of files so they can find their Excel files when they are looking for them. If you did not use the correct extension, both users and the computer will find it harder to find them and the computer may not open them properly.The .xls extension is the extension for Excel files up to version of Excel 2003. A computer will know what versions of Excel it refers to. It also makes it easier for users to identify types of files so they can find their Excel files when they are looking for them. If you did not use the correct extension, both users and the computer will find it harder to find them and the computer may not open them properly.The .xls extension is the extension for Excel files up to version of Excel 2003. A computer will know what versions of Excel it refers to. It also makes it easier for users to identify types of files so they can find their Excel files when they are looking for them. If you did not use the correct extension, both users and the computer will find it harder to find them and the computer may not open them properly.The .xls extension is the extension for Excel files up to version of Excel 2003. A computer will know what versions of Excel it refers to. It also makes it easier for users to identify types of files so they can find their Excel files when they are looking for them. If you did not use the correct extension, both users and the computer will find it harder to find them and the computer may not open them properly.
An Excel Book or Excel Workbook with the files extension of .xlsx
A file that has .xls, .xlsx, .xlsm as file extension then it is known as excel file.
On a handheld with Pocket Excel
Worksheets do not have extensions. They are contained in files known as workbooks. A 2007 workbook extension is .xlsx.
For a standard Excel document, prior to Excel 2007, it is xls and xlsx is used in 2007. There are other kinds of files created by Excel, like templates which can be xlt or macros which can be xlm and xla for Add-ins, and there are other extenions. For 2007, you add x to the end of them.
Excel files are usually .xls In Office 2007 Excel files that are single pages are still .xls while workbooks (more than one page) are .xlsx There are other extension for documents that are web pages in Excel, documents that have macros enabled and other such things. To find out, go to your Excel program and click "save as" When the menu comes up, click on the pull down menu "save as type" You will be able to see all the different options there.
It will depend on the specific type of file and version of Excel. The standard spreadsheet uses xls for versions up to 2003 and xlsx from version 2007. You can also have other types of files, like Excel template files, which would be xlt, or xlm for Excel macro files. There are several other types too.
The extension for excel is .xls