I am gonna be honest I am not entirely sure what you are getting at here... or any of us for that matter.
Are you wondering how to properly proportion your model in Blender so it is the correct size in game? If that is the case, I do believe that the standard cube in Blender (the one that shows up every time you start Blender) is a 1m X 1m X 1m cube.... I think anyways... That and I do believe that the underlying grid that you can see in Blender is measured in meters. So if you build everything with real life measurements in Blender, it should show up in game correctly proportioned and scaled.