Finding scale is easy.  If the scale model of a house is 18 inches wide and the actual house is 48 feetwide, the scale is figured as follows.

1.  Find a common measurement.  In this case, inches.  There are 12 inches in a foot so multiplying 48 x 12 = 576 inches for the width of the actual house.

2. Divide this number by the scale models total inches,  576 / 18 = 32 so there are a total of 18 sections which are 32 inches in length in the actual house  for a scale of 1:32 inch scale

3.  If you wanted to convert to feet per inch scale, simply divide the 32 inch sections by 12 (32/12= 2.666666667) for a scale of 1 inch : 2.666666667 feet