If you want a "scale size" for 1/48 scale, then you can start with 35mm which is equal to an average height person of about 5 foot 9 or 10 inches. If you have a good anatomy chart (most anatomy books have them or you can find one online, although all are not equal and it pays to look for a good one!), you can simply use a reducing or enlarging copier to scale it to the correct size. Then do the same for a full length photos or illustration of the figure you intend to do. This can then act as a diagram for placing all of the strategic points of the figure and for measuring width of belts and size of equipment etc. When scaling a clothed figure DO NOT count the heels of the shoes! Your anatomy chart will not have heels so these must not be counted to remain consistent.
Good luck!
Mike