We have found 4 software records in our database eligible for .xlsm to .xlsb file format conversion.
You actually do not need to look for some utility that would allow you to convert xlsm to xlsb. Simply re-save .xlsm spreadsheets to .xlsb files using the File ► Save as.. function in Microsoft Excel.
Some other spreadsheet programs might also offer xlsm to xlsb conversion via saving function, but it is always best to use the original program because of compatibility reasons and special formatting.
Updated: October 4, 2022
XLSM
Files with xlsm extension are used for workbooks of spreadsheets created in Microsoft Excel that also include macros, that enhance the functionality of the spreadsheet but some automation features. Other spreadsheets might open xlsm files as well, however they most likely wont be able to use the Excel specific formatting and macros.
XLSB
Files with xlsb extension is used by Microsoft Excel spreadsheet editor distributed with the Microsoft Office. An xlsb file contains Excel workbook stored in a binary file format (BIFF12). The BIFF12 binary format is used for data that can not be stored in the Open XML text format.