I have to scale down a building to make a model. No biggie there. Thing is – 1:75 seems to be the best size-wise.

So I’m sussing out how big this thing will need to be and I do this math:

[i]1m @ 1:100 = 10mm
1m @ 1:50 = 20mm

Therefor (in my head) – 1m @ 1:75 should be 15mm[/i]

But. It’s. Not. – it’s actually 13.3mm – and while I’m happy to accept that, it’s really frustrating me that I can’t get my head around the fact it’s not a straight forward linear progression.

Anyone got a good way to explain this to me? (preferably is poorly drawn MS Paint diagrams)

that’s your answer, you can’t tackle it as linear, it dimishing.

at the start, as you increase your ratio, 1:1 1:2 1:3, you get big changes in the scale unit size. but as you get to larger ratios, 1:50 1:60 1:70, the changes become much smaller, until you get to a point where increasing the ratio by hundreds, or even thousands, won’t make much difference to your scale unit size.

coz percentage difference in the scales (soz no diagrams)
100/75 is 1.33333333333333333333333333*
therefore 1:75 scale is 1.3333 x 1:100 scale (10mm x 1.333333 = 13.33333 mmmmmmmm)

or the other was around 1:50 scale is 75/50 = 1.5 x bigger than 1:75 scale (13.3333333 mmmmm x 1.5 = 20mm

100/50 is still 2 hence 1:50 is twice the size of 1:100