Standard Dimensions

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Short Definition

Dimensions that determine clearances between tracks, structures, platforms, etc.

The table below is clearance and dimensional information that you may find useful to have around. G scales have been split up into F, G, and A for better accuracy.

Standard Clearances, American Practice
Scale
Prototype
F
G
A
#1
O
S
H0
N
Z
Ratio, 1:
1
20.3
22.5
29
32
48
64
87.1
160
220
Track Centers
9.5
8.5
6
6
4
2.75
2
1
1
Track Centers, double curved trackage
10
10
9
9
6
4.13
3
1.5
1
Overhead Clearance
22
13.0049
11.7333
9.1034
8.25
5.50
4.125
3.0310
1.65
1.2000
Minimum Clearances, Track Center to Structures
8
4.7291
4.2667
3.3103
3.00
2.00
1.500
1.0222
0.60
0.4364

Notes: The track centers for double track on curves was derived from NMRA straight track practices. Refer to the NMRA Standards for more detailed information, as clearances are related to degree of curvature.

All dimensions are in inches, except those for the prototype, which are presented in Feet.

For more detailed info please refer to the NMRA Standard S8 Track Centers. Also see the NMRA RP-2 Standards Gauge. Good trackwork which meets the standard, and checking wheelsets and clearances with the gauge, will reduce derailments and other tracking problems.