This article lists the track and wheelset standards from historical sources in the UK and commonly-used standards in other parts of the world. The UK standards are the original standards for O gauge proposed by Henry Greenly in 1935, and the standards published by the British Railway Modelling Standards Bureau (BRMSB) in 1951. The BRMSB standards were the precursor to the Gauge O Guild standards [link required].

In North America the standards are those of the North American Rail Road Association (NMRA).

In Australia the standards are those of the Australian Model Railroad Assocation (AMRA).

In Europe the standards are those of MOROP, a coordinating body for various national model railway associations.

[1] BRMSB Unified was introduced in 1951 in an attempt to provide a universal set of standards for O gauge and allow a range of wheelsets to be used. G, FY and OC vary with the curve radius as follows:

• 5 ft radius and over: G=31.6, FY=1 .6, OC=28.0
• 5 ft -4 ft: G=31.8, FY=1.8, OC=27.8
• Less than 4 ft: G=32.0, FY=2.0, OC=27.6

[2] The NMRA Standard is published by The National Model Rail Road Association Inc. (The metric dimensions shown are the calculated equivalents of the Imperial ones). The NMRA standards quoted here are for standard wheels and track. Other NMRA standards are for Proto Scales and Scales with Deep Flanges. The NMRA standard was accessed on 2 March 2021.

[3] The AMRA Standard is published by The Australian Model Railroad Association. The AMRA standard was accessed on 2 March 2021.

[4] The NEM Standard is published by MOROP. The NEM standard was accessed on 2 March 2021.

The Guild track and wheelset standards

The standards explained

Scale and gauge equivalents of prototype gauges

This article was originally compiled by the Technical Committee and published in the Gauge O Guild Manual. It was updated and adapted for the GOGWiki by Nick Baines.