HO scale is the most popular scale for model railroading, partly because its size represents a good compromise. It’s small enough that you can fit a decent layout in a reasonable space without it taking over your basement. But it’s big enough that you can see it. But how big is HO scale? How big is an HO scale train?

## How big is an HO scale train?

Here’s how to do the math to figure out how big an HO scale train is. HO scale is 1:87, which works out to 3.5 mm on the model representing one foot on the real thing. A typical HO scale car is 140-175mm in length, or between 5.5 and 7 inches. If you buy a starter set, you can expect the train in the set to be around three feet long (approximately a meter) if it comes with a locomotive and about four cars.

You can expect the locomotive to be about 35 mm wide and 56 mm tall. Or in US measurements, about 1 3/8 inches wide and 2 1/4 inches tall. The cars will typically be a bit shorter and perhaps not quite as wide.

An HO scale train is approximately twice the size of a comparable N scale train, and theoretically half the size of an O scale train. Lionel trains don’t adhere very closely to standards. So an HO scale set can end up taking up about the same amount of space as a Lionel O gauge set, but Lionel sacrifices some scale fidelity in order to do so.

## How big is HO scale? How big is an HO scale layout?

But there’s more to an HO scale layout than just the train. The train needs track to run on, so the size of an HO scale layout is another consideration.

A circle of HO scale track has a radius of 18 inches. So a full circle ends up being 3 feet in diameter. If you buy an HO scale starter set, the oval of track it comes with will probably be about three feet wide and about five feet long when you put it together.

A popular size for HO scale layouts is 4 feet by 8 feet. That’s slightly smaller than a ping pong table. This gives you enough space to have some options for how you run your layout.

### HO scale in a 4×8 space

If you want to do some operations and build up trains in a yard like a real railroad, 4×8 is enough room for a small yard. If you just want to watch a train go in circles and relax, 4×8 is enough room to have a couple of trains going. It also allows them to do something a little more complex than just a circle.

### HO scale in 18 square feet

Another option is to do a shelf layout, with two tables on either side of the room and a long shelf with two lines of track connecting them. In the simplest setup, you just have a 3-foot table on each side and lay a circle of track for the train to turn around in. Add one short straight piece so the train can turn around. Finishing the layout is easy. Put a backdrop along the wall, then put some scenery and/or buildings on the two tables. The result is an HO scale layout in about 18 square feet.

Over time, you can add complexity if you wish. You can put a yard on one table and a town on the other, for example.

if I want to create an HO layout by building objects with a 3D printer, how do I get the correct scale 1:87 for the printed 3D objects? I mean, I know if I have a building that is 87 feet wide, the scale model will be 1 foot wide, but how do I do this without actually measuring the actual building using a measuring tape? I am thinking about using Autodesk’s Recap program to take a series of photos that are then stitched together, then Cura created the slices for printing on a printer, lets say a i3 Mega 3D printer? How do I get the final model the correct size without measuring the real buildings in real life?

Extrapolate the dimensions. If the building still stands, measure the door, then extrapolate the rest of the dimensions from a photo. If the building doesn’t still exist, you can approximate it by assuming the door is 7 feet tall. In a really simple example, let’s say you have a 2-story building where the door is exactly 1/3 the height of the rest of the building. In that case, if we assume a 7-foot door, the building is 21 feet tall.

Similarly, you can extrapolate the width of the door from the height, then get the width of the building. Just measure everything relative to that one known measurement. Make sense?

You know, I taught AutoCAD for 5 years and I should have remembered that door widths are a good universal standard for measuring! Thanks! (Also, do you do any 3D printer stuff?)

I’m interested in 3D printing but haven’t gotten one yet. I may when my sons get a bit older if one or both of them take an interest in it.

https://youtu.be/5cyB51H0LcA

Here are the videos I have done so far…

https://youtu.be/InCOK_2EPN4

https://youtu.be/xn8n1IdJkSA

https://youtu.be/R21w6NFf0-w