Calculus are very basic and you can do them by hand but if you want to convert a few tracks, life will be easier with this.
You just have to enter the values from your MXS terrain.hf and put the numbers that you get into your MXB .hmf file.
http://www.mediafire.com/file/e5pcgbnxg5kkz37/MXS_to_MXB_Terrain_Size_converter.rar
That's helpful! Thanks David. :)