What is the difference between 00 and H0?

If you have ever wondered into your local model shop to admire, dream about or even treat yourself to a 00 gauge loco, then you might have noticed a few of the engines on display are modelled in H0 gauge, even though they appear to be the same size as their 00 gauge counterparts, you may even notice that some of the buildings and scenery packs are labelled H0/00 gauge.

So what is the difference between H0 and 00 gauge?

To answer that question, we must first explain the difference between gauge and scale.

Gauge refers to the track, more specifically it refers to the distance between the parallel metal rails, whereas, scale refers to the size a model is in relation to its full-sized prototype.

Both H0 and 00 trains run on the same gauge track measuring 16.5mm between the rails, however, the scales of H0 and 00 engines are different.

H0 engines have a scale of 1:87, this means that the full-sized engine that the model is based on is 87 times larger than the model.

00 engines have a scale of 1:76, that means that this time the full-sized engine that the model is based on is only 76 times larger than the model, or to put it another way 00 scale engines are bigger despite running on the same tracks as H0.

The reason for this dates back to very early models and a need to overcome a manufacturing dilemma. At the time H0 engines were mainly emulating US and continental prototypes. These were much bigger engines in real life, therefore space was abundant on the models to fit mechanisms into their casings. Real-life British locomotives, however, were a lot smaller by comparison. This inevitably led to the model casings being too small for the primitive mechanisms to fit. The solution was to make the casings (outer bodies) of the models slightly oversized and 00 scale was born.

This generally meant that British engines were modelled in 00 scale whilst US and continental engines continued to be modelled in H0 scale as it is technically more accurate.

Because modellers will often be drawn towards models of engines from their native countries (when available), it is perhaps not surprising that 00 scale has over the years become the scale of choice for the British whilst H0 scale is preferred by our modelling friends over in the States and continental Europe.