O gauge vs O27 gauge trains and track

Last Updated on September 11, 2022 by Dave Farquhar

The difference between O gauge and O27 gauge can be rather confusing, and there are a number of misconceptions out there about O27 especially. Let’s take a look at O gauge vs O27.

O27 always had a connotation of being a cheaper, entry-level train. But what constitutes an O27 train in modern times definitely varies from the 1950s. Lionel discontinued both O and O27 track types in 2015, after approximately 100 and 85 years of production, respectively.

The difference between O gauge and O27 gauge track

o27 gauge vs o gauge track
The track on top is O gauge. The track on top is O27 gauge. The rails are the same distance apart, but the O gauge track is made from heavier metal.

A full 1:48 scale O scale train requires a circle of track 72 inches in diameter to work reliably. No parent in the 1930s was going to buy a toy for their kids that required a minimum of 36 square feet to set up a boring circle. So companies like Lionel, American Flyer, Ives, Marx, and others compromised. They did some selective compression and eliminated detail so their trains could run on a much smaller circle of track.

In the United States, the two most common diameters of track ended up being 27 inches for smaller, less expensive trains and 31 inches for slightly larger, more expensive trains.

Both types of track have a distance of 1.25 inches between the outer rails, and both have a center third rail, but there are some differences in the track itself.

O gauge track stands 11/16″ high from the bottom of the tie to the top of the rail. O27 track stands 7/16″ high, also measured from the bottom of the tie to the top of the rail. O gauge track is made of a heavier gauge metal, which makes it very durable and more highly conductive. This makes it popular, even though it is grossly oversized.

Standard O27 straight track sections are 8.875 inches long. O straight sections are 10 inches long. Longer sections of each type are available. Typically they are around 3 feet in length but the precise length can and does vary.

Here’s a compilation of all the relevant dimensions of O and O27 track.

Both types of track use 8 curved track sections per circle, with each piece making a 45-degree turn. You can get wider-diameter curves as well.

You can mix between manufacturers. Lionel, K-Line, and Marx O27 track will all work together. The only thing you need to be really careful about is switches. You can mix different makes of O31 track too. Lionel, K-Line, Menards, and other makes of O31 track work fine together. You can mix makes easily. Mixing O27 and O31 track takes a bit of tinkering. It’s possible but I don’t recommend it.

The difference between an O gauge and O27 gauge train

o27 gauge vs o gauge cars
The black gondola on the left was an O gauge car from the 1950s. The shorter blue gondola on the right was an O27 car from the early 1960s. The cars in the background are even smaller-sized O27 cars from the late 1930s.

O27 train cars were always shorter than their larger O gauge counterparts. Prior to World War II, O gauge train cars could be as big as 10 inches long, while O27 cars could be as short as 6 inches long, although a range of 6-8 inches was fairly common. There was a similar difference in the size of the locomotives.

The trend followed into the 1950s. The popular Lionel 6464 boxcars were O gauge in the 1950s. Lionel marketed the smaller 6014 boxcars as O27. For a time, O and O27 trains even had incompatible couplers, but Lionel stopped doing that after they realized it discouraged upgrading.

Lionel sometimes sold the same locomotive as both an O gauge and O27, just changing the number on the cab. Lionel didn’t always follow this convention, but usually a 3-digit number indicated an O gauge locomotive and a 4-digit number indicated an O27 locomotive.

There is never any problem running O27 trains on larger O gauge track. If anything, the O27 trains work better on the wider diameter track. Some O gauge trains work fine on O27 track, especially if there was a version of it for O27 track. For example the Lionel 675 works fine on O27 track, just like its identical counterpart, the 2035.

Traditional O27 Lionel vs modern O27

Today, hobbyists often call anything smaller than full 1:48 scale, including 6464 boxcars, O27. A 6464-sized boxcar will indeed run fine on O27 track, so there’s nothing wrong with calling it that. The terminology has evolved since the postwar era so keep that in mind if you’re reading both recent and vintage books about Lionel.

Pretty much since the very beginning, Lionel and its competitors like American Flyer and Ives made trains in multiple sizes but running on the same track. By the late 1920s, they had all pretty much settled on two or three sizes of trains. The smaller trains, which ran on O27 track, had cars that were about 7.5 inches long. The bigger ones were 9 or 10 inches long.

Lionel continued this in the postwar era. The smaller trains were O27, and most O27 cars, especially the boxcars and gondolas, were about 1:64 scale. That’s right, they were S scale cars on O gauge trucks. Flyer guys have been buying those cars out of junk boxes, repainting them, and putting S scale trucks on them for years. The blue Lionel gondola pictured above is exactly the same length, width, and height as a Flyer gondola.

The larger trains in Lionel’s postwar era were generally around 9 inches long, a little too small for proper 1:48 O scale. They were really closer to 1:56 scale. Once Lionel started making 1:48 trains, it started marketing the older cars as O27, because those cars happen to run fine on O27 track. So when someone says O27 is bigger than 1:64, they’re referring to those 1:56 cars. But if you hold a postwar Lionel Baby Ruth boxcar up against a postwar Flyer boxcar, you’ll note the width and length are almost identical. The Lionel car is taller, but the Flyer car was modeled on a shorter-than-normal prototype.

O gauge vs O27 gauge

I’ve had many an enthusiast roll his eyes at me when I say O27 track is worth considering, but hear me out. You can buy wider diameter curves and switches in both O and O27 profiles. I have O27 track, but most of my curves are 42 or 54 inches in diameter. O27 straight sections are cheaper than O gauge sections. In my case, I had tons of O27 straights that had belonged to my dad and I didn’t want to throw it out. By buying wide curves, I got the benefits of the wider track without having to replace everything.

O gauge track is heavier gauge metal so it is more durable and has less voltage drop, but it stands a foot taller on the layout. I find it amusing when people gripe about not being able to find enough 1:48 vehicles and having to settle for 1:43s in one breath, then belittle people for using O27 track in another.

I use O27 track and just run a couple more feeder wires than I would have otherwise. It’s worked well for me for almost 15 years.

So there are some differences in O gauge vs O27 gauge, but don’t write off O27 entirely. You may very well find it works better for you than you might have thought.

O gauge gives plenty of opportunity for confusion, so here’s a glossary that can help with some other terminology.

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