HO Scale. HO scale comes is a scale of 1:87. It is currently one of the most popular modeling sizes in model railroading. It is approximately half the size of O scale, hence the name HO (half of O). Because it half the sized of O scale, obviously, you can add more detail and longer trains in a smaller area. HO Scale has been a favorite scale for many modelers for years and it introduced many to model railroading. While n scale may let you run longer trains, HO can me more user friendly on the eyes. Also being one of the more popular scales, the selection is huge. Adding detail, kit bashing and scratch building is also easier than the smaller scales.