You just enter the dimensions it asks you for, i.e. Material Thickness, Diameter, Height, etc. The Calculator does all the math and you just transfer the output dimensions from the calculator’s Large Screen to the Material, and it’s “DEAD ACCURATE”. The output dimensions are shown in decimal form first, and in the fractional form second to the closest 32nd of an inch +/- 1/64th. The 120-plus page “Visual Manual” was written for the person that can read and understand a drawing easier than reading instructions. Visually there is no guessing.