When you are new to the model trains hobby, all of the size choices can be confusing. The first time you see an "N" or a "G" in the name of one of the trains you may think it is a typo, but those letters contain very important information about the size of the model. It represents the scale, or the size of the model in relation to the actual train. A model that is 1:29 scale is one 29th the size of the actual train. Gauge refers to the size of the railroad track. This hobby is popular all over the world so the sizes are pretty standard regardless of where you are shopping. The scale classes break down like this:
G Scale Sometimes referred to as garden scale, these trains are some of the largest reproductions. The G comes from the German word for big, gro . The scale is 1:22.5 but they can range up to 1:29. They are referred to as garden scale because many people opt to use them outside due to their large size. At about 8 inches tall, their equipment doesn't fit well inside most homes and many hobbyists enjoy planning their landscaping around their train and track anyway. G-scale trains typically run on a 45mm gauge track.
O Scale These trains are 1:48 scale and run on 31.8 mm gauge tracks. They are noticeably smaller than G-scale trains but still look large to many hobbyists, who usually opt for smaller models. The O-scale trains were once very popular, especially for children, so many of the antique model trains you see are this size. Also, this is still regarded as a great size for children.
S Scale This size originated with the American Flyer brand of model trains, which was very popular in the 1950s, and is about halfway between the O and HO size. These models are 1:64 scale and run on an 11.4mm gauge track.
HO Scale By far the most popular size for model trains, the HO scale is big enough to offer a lot of detail in the reproduction and yet small enough that most people can find a spot inside their homes for their track. This also is the most widely produced size so there are lots of trains and accessories to choose from as you expand your set. The HO scale is 1:87.1 and they run on 16.5mm gauge track.
N Scale These trains are popular as well because they are very compact 1:160 scale that runs on 9mm gauge track. N-scale locomotives are about the height of two pencils stacked on top of each other. Their smaller size means you can fit a complicated track layout into a relatively small area. They are especially fun for those who like to work with the scenery along their track and care a little less about the detail on the actual train.
There are also less common sizes in between those main categories, including the T scale, which has only been on sale since 2008. Those trains are 1:480 scale, which means individual cars are not even as long as an average index finger.
The best size of model train for you or your loved one is the one that will best suit interests. Larger-scale models offer much more detail on the actual train, but a smaller-scale model allows you to more easily craft an obstacle course of tunnels and mountains for your train to weave in and out of. You may also want to consider what space in and around your home that you can set aside for the hobby. A G-scale model needs more room to roam than a tiny corner of the basement. A little thought about your specific situation will ensure a wonderful experience with the model trains hobby.