This article was published May 17, 2012.
One foot is 12 inches, 1 inch is 25.3945mm, making one foot 304.734mm, that's your 'base' to work from. All these scale proportions are relative to one foot.
So, for example my 3n20 scale, take one foot divide with 16, the model is 16 times smaller than in real life or 1/16.
The other way, 1/24 is 1/2in scale, because one foot divided 24 times makes 1/2 inch.
Next. What is 3/8in scale? First we must convert 3/8 inch to mm which is 25.3945 / 8 * 3 --> 9.5229375. Now again, take one foot / 9.5229375 = 1/32.
Don't ask me who invented this, it's just is.. but, if you are used to feet's and inches it might sound easier... I do not know.
- One yard = 3 foot = 914.2045 mm
- One foot = 12 inches = 304.7348 mm
- One inch = 25.3945 mm
Another example; How many inches are N tracks in 0 scale? First 0 scale is 1:48 ratio and N scale gauge is 9mm, so we take 9 * 48 = 432mm in real life. Next we divide 432 with 25.3945 (one inch in mm) equals 17.011... and alot decimals. Conclusion, N scale tracks are 17 inch gauge in 0 scale.
Now there exist different ratios of O-scale depending on where you live. In UK O-scale is 1:43.5, here in Sweden O-scale is 1:45 the same for most of Europe. In US it's 1:48. Just exchange the ratio in above calculation according to your needs.