Facts and Figures

Model Railway Scales and Gauges

Scale	Ratio	mm/ft	in/ft	Gauge mm	Gauge in	Notes
Z	1:220	1.4		6
N	1:160	1.9		9
N(B)	1:148	2.1		9
OOO	1:152	2		9.5		1
TT	1:120	2.5		12
TT(B)	1:102	3		12		2
TT(C)	1:100	3		13		3
HO(C)	1:90	3.4		16.5		4
HO	1:87.1	3.5		16.5
HO(C)	1:85	3.6		16.5		5
HO(C)	1:82	3.7		16.5		6
OO(B)	1:76.2	4		16.5
EM(B)	1:76.2	4		18
P4(B)	1:76.2	4		18.8		7
OO(A)	1:76.2	4		19
S	1:64	4.8	3/16	22.2	7/8
Q(A)	1:48	6.4	1/4	30.2	1 3/16
O(A)	1:48	6.4	1/4	31.7	1 1/4
O(C)	1:45	6.8		32		8
O17(A)	1:45	6.8	17/64	31.7	1 1/4
O	1:43.5	7		32		8
1(A)	1:32	9.5	3/8	44.5	1 3/4
1(B)	1:32	9.5		45
1(C)	1:30.5	10		45

The table above deals with models of Standard Gauge trains i.e. models of trains that run on 1435mm (4'-8 1/2") gauge tracks. (A) means North America; (B) Britain; (C) Continental Europe, and the most popular commercial gauges are shown highlighted. Some of the others are uncommon but may turn up when dealing with second hand or collectors items.

Notes

Has largely been supplanted by N
Also known as TT3
Used by Swiss firm of Wesa
Was used by Trix Express in the 1960s
Used by Fleischmann for European Models
Was used by Fleischmann and Ravarossi in the 1960s
Also called Protofour
1:45 is a standard scale on the continent but 1:43.5 is also used in France, as well as Britain.

Of the scales in the OO/HO family, only HO with a scale of 1:87.1 is strictly correct for 16.5mm gauge track. The other scales in the family are hybrids and have mostly come about due to technical limitations e.g. the size of the available electric motors at the time they were developed.

This article is copyright (C) Andy Slater and is used here with permission