Scales used for Garden Railways

Any railway laid round a garden can be called a garden railway, but the
multitude of scales for Garden railways can be quite confusing.

Today the term 'Garden Railway' or 'G Scale' is normally applied to Gauge I, IIm or SM32 and SM45. ( G Scales table)
Gauge 'I', though using the same 45mm track gauge as IIm scale, is quite different - Gauge '1' models are of standard gauge railways while IIm Scale models are of narrow gauge railways.

IIm scale, SM32 and SM45 are normally grouped together as size compatible, despite the scales being slightly different. Though they have two different gauges, 32mm and 45mm, all three represent narrow gauge models and have similar overall sizes of locomotives and stock.

In the USA, the situation is a little more confusing, as they also have 1/2" and 5/8" scale narrow gauge using 45mm gauge track which can be run along side the above mentioned.