Geep, maybe I changed them at some point, but my default settings are set to "feet", which seems to make ericwiz's original answer of a "yard" (3 feet) per square accurate. Again, I probably changed it from the factory state somewhere along the way and forgot I did it. LOL. ;-)

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Tools :  3dsmax 2015, Daz Studio 4.6, PoserPro 2012, Blender v2.74

System: Pentium QuadCore i7, under Win 8, GeForce GTX 780 / 2GB GPU.