... it, because that makes it easy. The size of the plan in cm when printed is irrelevant because that depends on your printer settings and the software which you use to print it. The information needed for Templot is the size of the image in pixels (dots). However, your scan included a lot of empty white space which would slow down the screen response in Templot. So I have rotated it for a better fit on the screen, and cropped it down to 3000 x 1000 dots, like this: 2_172244_550000000.jpg I then used a screen pixel ruler to measure the distance between the 16ft marks, and the answer is 2702 dots. If you don't have a pixel ruler, you can get a free one from: http://www.spadixbd.com/freetools/jruler.htm (Alternatively, you could use the crop/combine function to crop the image in Templot to the 16ft marks and then read the number of dots shown below the background shapes list.) We now have enough information to calculate the model size of the full 3000 x ...