You need to know the scale of the model that you are working with. Most full-sized card armour models are 1:25 scale, and card aircraft are 1:33. If you do not know the scale, either contact the designer or get a good scale drawing of the prototype (1:1 scale)and take some measurements. The formula to REDUCE SCALE is ( Original / Reduction = New Reduced Size), or . (O/R=NRS) Therefore, to REDUCE 1:25 scale to 1:35 scale is (25/35 ) = 71% (0.71) The formula to ENLARGE SCALE is (Enlarged/ Original = New Enlarged Size) or( E/0 = NES) Therefore, to ENLARGE 1:35 scale to 1:25 is (35/25 ) = 1.4 (140%) For example: to REDUCE a 1:25 model to 1:32, we apply the formula (25/32 )=NRS 78%

Why do the work yourslef when there is a great little program available. It even tells you the enlarge/reduce factor in % terms on a photocopier or pdf file print setting. scale calculator