Model Railway Beginners Q&A: What's the difference between scale and gauge - Model Railway Engineer

Model Railway Beginners Q&A: What’s the difference between scale and gauge

2 comments 2 Beginner's 2 Comments

model railway track scaleIf you’re just starting out in model railways one question that’ll you’ll invariably want answered is what are scale and gauge? What’s the difference between them and should you worry about them?

When it comes to buying and running model railways you’ll often come across guage and scale. These two innocuous sounding words relate to the size of your model railway and although often used interchangeably they mean very different things and shouldn’t be confused.

Gauge

I’l start with Gauge, for no other reason than it’s the easier of the two words to understand.

Just like full size railways, the gauge of your model railway measures the distance between the rails on track.

There are four track Gauges commonly used in UK railway modelling. From largest to smallest these are:

  • 45mm Gauge: Commonly use for garden railways.
  • 32mm Gauge: Often very realistic looking but can be expensive.
  • 16.5mm Gauge: The most common track and engines in the UK.
  • 9mm Gauge: The smallest, allowing more track to be laid in the same area.

Scale

LMS 4-6-0Scale is the ratio between the size difference of your model to its real-world equivalent. The models you see on model railways aren’t just shrunk until they look about right but are all accurately reduced versions of their real life counterparts, with every part reduced by the same amount.

The common model railway scales being:

  • O scale – 1:48 Needs lots of space and great for kids as the parts are big enough for children to handle easily. Works with 32mm gauge.
  • OO scale – 1:76  By far the most popular in the UK and uses 16.5mm guage.
  • HO scale – 1:87  This size offers highly realistic layouts within a relatively small space, not as popular in the UK as OO but works to same gauge.
  • N scale – 1:148 or 1:160 The second smallest train size and my personal favourite as it allows for great scenery but the small size makes it sometimes difficult to work with and the engines and parts aren’t as common or cheap as OO and HO. Runs on 9mm gauge track.

So is it Scale or Gauge?

Now you’d be forgiven for thinking that if every object in a model railway was shrunk to the same scale then the tracks would be the scaled down to the same degree as the rest of the set so the rails would be proportionately same distance apart as buildings and figures are to the train.

Sadly not.

For a variety of reasons, the scale factor used to get set the distance between rails is often slightly different to the scaling factor used for the rest of the models so we end up with railway scale and a track gauge.

And, it’s possible to buy two trains with the same gauge but with different scales. OO and HO scales being the most obvious. These both use the same Guage of track – 16.5millimeter – but OO models are slightly larger than HO (HO standing for Half O).

In most cases this is difference is hardly noticeable but if you’re a stickler for accuracy and want your railway set to look just right it’s always worth checking that your purchase has not just the right guage for your track but the same scale ratio as the rest of your layout.

TIP: If you’re looking for a guide to tunnel sizes for different sizes, Elgin Model Railway Club have a done a great guide here

This post is part of my beginner’s guides. For more like it see my parent post, beginner’s guide to model railways.



PS, If you liked this, join over 20,000 model railway fans and sign up now to get my unique guides and tips. It's completely free, you can unsubscribe at any time and I promise to never spam you. Sign up here.

 Picture: Track, J. Rygh.

 

 

 



  1. Andy MacCabe - April 27, 2016

    OO Scale is 1:76, not 1:87 as you claim above. I’m surprised no-one has commented on this before.

    OO Gauge
    4mm to 1 ft, 1:76 scale
    16.5mm gauge
    OO is by far the most popular gauge in the UK, although the gauge is 15% under scale.

    HO Gauge
    3.5mm to 1ft, 1:87 scale
    16.5mm gauge
    The same gauge as OO, but with the smaller scale the gauge is in correct proportion to the scale.

    • Andy, thanks! The page was updated recently swapping the order in which the gauges are listed, HO and OO changing. I must have copied/pasted the OO and HO lines wrong then hence why it’s not been commented on previously. My bad. Thanks for pointing this out.

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