Regina Railway Modellers Association
MODEL RAILROAD SCALES
There are many scales in which you can model trains. The smallest common scale is Z scale (1:220) and the largest indoor scale is G scale (approx. 1:24). The three most common scales are HO, O and N scales. The table below lists each scale and its ratio (e.g. 1:x where 1 inch on the scale model represents x inches in real life).
Let's say we have a GE ES44AC model. This is a photo of the real thing used to illustrate scale.
Z scale
N scale
TT scale
HO scale
S scale
O scale
G scale
The table below lists each scale and its ratio (e.g. 1:x where 1 inch on the scale model represents x inches in real life).
SCALE   RATIO   SCALE   NOTES
Z   1:220
  1/16 inch to 1 foot    
N   1:160   5/64 inch to 1 foot
   
TT   1:120   3/32 inch to 1 foot    
HO   1:87   1/8 inch to 1 foot    
S   1:64   3/16 inch to 1 foot    
O   1:43/1:48   1/4 inch to 1 foot   1/43 in Europe; 1/48 in North America
G   1:22.5   1/2 inch to 1 foot   Size varies according to manufacturer
             
HOn3   1:87       HO scale rolling stock on narrow guage (N scale) track
On3   1:43/1:48       O scale rolling stock on narrow guage (HO scale) track
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