The formula for ENLARGING is E= L / S, where L is the larger scale, and S is the smaller, and E is the percentage enlargement. The formula for REDUCING is R= S / L, where R is the percentage reduction. Decimal equivalents of common scales: 1: 87 = 0.0115 1:72 = 0.0139 1:50 = 0.0200 1:48 = 0.0208 1:33 = 0.0303 Therefore, for example, to REDUCE 1:33 to 1:72 = 0.0139 / 0.0303 = 0.4587 = 46% Fishcarver

You don't even need to reduce those to decimal equivalents. All you need to do is divide the lower part of the scale by the lower part of the other scale. Just use the calculator function on your computer and try this: 33/72=.458333333... equals 45.8% 72/33=2.1818181... equals 218.18% Ryan

I too am math challenged - for example if you know the circumference how do you figure diameter? Anyway, I just have this scaling chart at my desk - http://www.wwi-models.org/misc/scalecon.html

Oh great!! :twisted: Being in my mid-40s with a 2 year old, I'll probably be dead before I get to see these again. Thank goodness I have you guys to get my math formulas for me. hehehe :lol:

Hi, Then you take your increases/decreases along to a photocopier and do your photocopy enlargement reduction, bearing in mind that each page you enlarge and/or reduce will conform and be consistent to all other pages photocopied then. If the enlargement is too big for the photocopier, use your Square Root symbol on the calculator to downsize the enlargement into 2 increases. That is you photocopy enlarge to the first increment, then you take that (new) photocopy enlargement and enlarge it to the next and final enlargement by that same increment. J77ason