Standard Dimensions

Summary: 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.

Prototype distances are in FEET, all others in INCHES.

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.

Prototype Track Gauges

A number of gauges are in use around the world, see the Track Gauge page for more details.

Videos

All About Standards For Beginners