What's Gauge?
Gauge is the width of the track. Only trains that fit the track will run on it.
Which Gauges Are Most Lionel Trains?
Most Lionel trains run on two similar, related track gauges: O gauge and O-27 gauge.

What's the Difference?
Curves in O-27 gauge are tighter than in O gauge. That means that some of the very longest O gauge cars and locomotives are too long to turn the tight corners of O-27 gauge layout. All O-27 gauge cars and locomotives will work on O gauge track.

Lionel trains and track come in different gauges. Lionel O gauge and O-27 gauge trains are our most popular. We also sell S gauge American Flyer trains, which are slightly smaller, and G (garden) gauge trains, which are slightly bigger. When shopping for a train or train set, be sure to choose products that are designed to work together. Usually that means they need to be the same gauge.

If you're new to model railroading, you might be wondering, "What exactly is Gauge?" That's simple. Gauge refers to the distance between the outside rails of your track. (Your train's wheels roll along these two rails; the third, or "inside," rail is for power.)

O and O-27 gauges
Lionel manufactures two kinds of three-rail track -- Lionel O-27 gauge and Lionel O gauge. Both are actually the same gauge -- 1 1/4 inches between the rails -- but serve slightly different needs.

Lionel O-27 gauge track makes tighter curves than O gauge. Assemble O-27 curves into a circle and you get (surprise!) a 27-inch diameter circle. If your railroad has limited space, choose Lionel O-27. It's value-priced, offering various curves and crossovers as well as manual and remote-control switches. O-27 comes standard in all Lionel ready-to-run starter sets.

Lionel O gauge track comes in wider curves for bigger trains and layouts. The smallest circle it can make is 31 inches in diameter. O gauge also has a slightly taller profile for deeper wheel flanges. Lionel O gauge is designed to fit virtually all Lionel locomotives and rolling stock, including scale-proportioned pieces. Some larger Lionels will run only on O gauge track.

Gauge vs. scale
As you now know, gauge refers to track size. Scale, on the other hand, measures the size relationship between a model and its real-world prototype. For example, a Lionel locomotive that is 1/48th the size of the real thing is called 1/48th or 1:48 scale. (As it happens, O gauge trains are 1/48th scale.) Sometimes the terms "gauge" and "scale" are used interchangeably even though, technically, they're different.

Find out about Other Gauges.