What Does HO Stand for in Model Trains?

Getting into all things model train sets can not only be a great hobby but it can help you build important skills as well. Still, there is a bit of a barrier to entry when you consider all the scales and gauges and what they mean. In this case, what does it mean for a model train set to be built at an HO scale or have a track with an HO gauge? 

When it comes to model trains, HO stands for “half O-scale.” This simply means that the train’s ratio in size compared to the real thing is 1:87. That is roughly–though not exactly–half the size of O-scale model trains. Additionally, the HO gauge will be roughly 16.5mm wide. 

If you’re in the market for an HO scale model train or you’re just curious about the topic, this is for you. In our guide below, we will take a deep dive into everything related to HO model trains. We will discuss the difference between HO scale and gauge, as well as practical details like what kind of voltage it takes to run an HO scale set. So come along and let’s jump right in!

When Were HO Scale Trains First Developed?

Before we dive into everything you need to know about HO scale trains, it would be a good idea to get some background on how exactly they came about in the first place. HO scale trains have a fascinating history that reaches all the way back to the great depression.  

HO gauge tracks and scale trains were originally developed in The United Kingdom as a more economically viable alternative to OO scale trains. By the late 1950s, they had spread to the United States and become wildly popular amongst hobbyists and the model train community at large. This was perhaps due to their sleek designs, desirable size, and attention to detail. 

By the sixties, major manufacturers of model train sets like Lionel took notice and began releasing their own HO scale sets, propelling them to become a rival to the already well-established O scale sets. 

popular model train scales

Why is HO Scale So Popular?

So what was it about HO scale sets that separated them from the competition and made them so much more popular than other sizes?

The biggest factor in why HO scale trains are so popular is probably because they are just the right size. They aren’t so small that you can’t get vivid details on them, and they aren’t so big that they’ll take up too much space. They’re just right. 

With an HO scale train set, you can have almost all the detail you would have on a larger set but you also don’t have to sacrifice as much space. Further, with the space you save you can make your setup more intricate and varied. It’s really a win-win. 

What is the Most Popular Model Train Size? 

Today, HO scale sets have taken their place as the most popular available on the market. Of course, that’s not to say that other scales aren’t still popular as well, they just haven’t been able to catch up with HO. 

What’s the Difference Between HO Scale and Gauge?

While you’ve undoubtedly heard of HO scale–why else would you be here–you’ve probably also heard people refer to HO-gauge. If you’re new to working with model train sets you may wonder if these are synonyms for one another or if they refer to different things. Don’t worry, you’re not alone and we can help clear things up for you. 

Below we’ve broken down both HO scale and gauge to highlight their differences and explain how they work together: 

  • HO Scale: Scale refers to the size of the train set in relation to the real thing. In the case of HO scale, the model has a ratio of 1:87. This is compared to the actual train itself. Of course, this scaling rule should also apply to the pieces you add to the set itself so that everything looks like it has the proper proportions. 
  • HO Gauge: Gauge deals with how far apart the rails are from each other on the track itself. This will be related to the size of the train, however, it does not directly have to do with it. We will get into this in more detail in the following section, however, for now, suffice to say that there is some wiggle room on what gauge you use with what scale. 

As you can see, gauge and scale are closely related, however, they are not the same thing. One has to do with the train itself and the models around it, while the other has to do with how wide the tracks are. While in most cases you should match the gauge to the scale, you don’t always have to. We’ll dive into why that is in the next section. 

Can HO Trains Run On Tracks With Differing Gauges?

So, let’s say you buy an HO train but you mistakenly get a track for it, that’s another gauge. Will the HO train be able to run on the track without any major modifications or do you need to get a whole new set of tracks that match the scale? 

The truth is HO trains can run on most OO gauge tracks but not really any others. At least not without making major modifications. That’s because OO gauge tracks are the same width as HO tracks–coming in at about 16.5mm.

An important caveat here is that the depth of metal on the rail can vary and may not be as well suited to an HO train. If you have a newer model keep an eye out for code 75. If your model has a few more years or decades on it, however, you should keep an eye out for code 100, as it is most likely what you need. 

model train price

How Do HO Scale Trains Compare to Other Sizes?

When picking your first–or simply a new–model train set, it’s important that you compare and contrast the different scales so that you can pick the one most suited to your needs. To properly do this, you need a little background information on what distinguishes similarly scaled models. 

In the sections below we have attempted to answer the most common questions people have when comparing HO scale model trains with other similar sizes: 

Which is Better: HO Scale or O Scale?

So we’ve already established that O scale train sets are bigger than their HO scale counterparts. Twice as big in fact. Still, that doesn’t really tell us which is the better deal. So really, which is better at the end of the day, HO scale or O scale? 

While one could argue that HO scale sets are slightly better because they are more popular and easier to fit in a room, which one is actually better really comes down to the individual and what they value.

With an O set, you’re going to get more power and greater opportunities to add fine details. With an HO set you’re still going to get excellent fine details, but you will also save some space and possibly some electricity. It really comes down to you. Which do you prefer?  

Is N Scale the Same as HO?

Due to the fact that N scale and HO scale are both smaller than O scale, there’s a common misconception that they are two terms for the same thing. They are not. 

N scale is not the same as HO. N scale is to HO as HO scale is to O in that it is roughly half the size. N scale is typically about 1:160 when compared to an actual train and is one of the smallest scales that there is.

Interestingly, N scale has begun to grow in popularity in recent times. Perhaps they will have a boom similar to that which HO scale had during the late fifties and the sixties. 

Which is Bigger OO Scale or HO?

Another point of confusion many people have when they’re first getting into model trains is understanding which is bigger; OO scale or HO. 

OO scale sets are bigger than HO in that their ratio to real trains is about 1:76. The difference in size to that of HO scale–which, again, is about 1:87–is not as dramatic as the difference in size between other scales like O or N. Therefore, it is understandable that these two scales are often confused for one another. 

expensive model train

Are All HO Scale Trains Compatible?

If you do decide to go with an HO scale set, you’re also going to need to get some tracks. When you start looking for them you will likely be bombarded with all kinds of different options from different model railroad companies. Therefore, it is only natural to ask if all of the HO scale trains are compatible with all HO gauge tracks? 

Fortunately, all HO scale trains should be compatible with all HO tracks. Still, different companies develop different ways of making their tracks connect with one another, so it’s a good idea to pick one brand and stick with it. 

If you’ve already bought different sets of tracks from varying companies, don’t worry. While the tracks may not connect properly right out of the box, there are almost always modifications you can make to allow them to link up anyway. It’s just going to take some extra elbow grease. 

What Voltage Do HO Scale Trains Typically Run On? 

To really get the show on the road–or tracks so to speak–you’ve got to have some electricity running through the set. You don’t want too much or too little because at the very least it could cause your train to run in a way that looks unnaturally fast or slow, and at worse it could be a safety hazard. So, what is the appropriate voltage for HO scale trains? 

Most HO scale trains are going to be running on around 16 volts. That will save you some electricity when compared to other scales like O which run at around 18 volts.

Of course, you’ll want to make sure all the wiring is properly done ahead of time so that when you start your train there aren’t any hiccups. 

What Kinds of HO Scale Kits Can You Get?

Buying a scale kit is really the way to get your model train setup going. That said, there are different kinds of scale kits out there that are generally aimed at different levels of experience. Before you pick the right one for you, you should really take some time to consider how much of a commitment you are ready to make to this new hobby. 

Below we’ve outlined the three most basic kinds of kits available in the HO scale so you can pick the type most suited to your needs and skill level: 

  • Shake-the-box train sets: We’ve listed these kits first because they represent the happy middle ground in terms of the skill level it takes to assemble them. You’ll have some simple parts to assemble first to create an excellent little train, possibly with a freight car or something else with it. 
  • Craftsman train sets: These require the most skill to put together, however, they also tend to lead to the most satisfying payoffs when they’re done. If you get one, you’ll have to pour through tons of both small and large parts to slowly assemble your model. Because it is made of so many parts, it often looks more detailed and convincing. 
  • Ready-to-run train sets: Lastly, if you just want something that is easy-peasy, then go with one of these ready-to-run model train sets. You can practically pull them right out of the box and get your setup done in no time.

If it’s your first time building a model railway, it’s a good idea to get your feet wet with one of the simpler kits and work your way towards the craftsman ones. Still, if you’re one of those people who likes to dive right into the deep end of the pool, you’re more than welcome to start with something more challenging. Whatever you do, have fun with it!

So Really, What Does HO Stand for Model Trains?

Whew! Let’s recap since that was a lot of information in a small space. HO stands for “half O-scale.” While that might make you think that HO is simply half the size of O, in reality, it’s a little over half that size. HO scale has a ratio of about 1:87 when compared with the real deal, whereas O is about 1:48. If HO was truly half the size of O scale it would be 1:96. 

So now it’s all up to you. Pick out a train kit, make sure you get the right gauge track and a power supply with the appropriate voltage and get started! What will you create?


Lifelong Rail Enthusiast and Owner of Worldwide Rails

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