Scale measurements defines the ratio of model size to actual size.

Scale-----Defines the ratio of model size to actual size. For instance, 1/4 inch scale means 1/4 inch =1 actual foot. Since there are 12 inches per foot, 12 x 1/4 =48. 1 actual foot=48 scale feet. This is defined as 1/48 scale or 1:48.

Gauge----- Distance measured from the inside of a rail to the inside of the adjacent rail. For standard gauge American railroads this is 4ft. 8 1/2 in. O gauge (1/48 scale) specifies this distance as 1 ¼ inches. 1 ¼ in. actually scales to 5 ft

To make measurements in your scale, simply multiply the actual length of the prototype by the appropriate factor. A 40 ft. boxcar in HO will be: 40x.138 in. =5.52in. Or 40x3.5m=140mm.

In some cases it is more practical to use the nearest fractional value to define the measurement. For instance, an HO ft. is approximately 1/8 in. Using this factor, 1/16”=6”, 1/32”=3”, 1/64”=1 ½”. If you need 4”x 8” stripwood, not many will notice if you use 1/16” x 1/32”.

The most popular gauges are HO, N, and O. I model in HO because when I started 50 years ago it was the best option in terms of space requirements, availability of equipment, and cost. I would have loved to model in O gauge, but the cost and space requirements were out of reach. Today, HO is still the most popular with more manufacturers, kits, rtr equipment and information than any other gauge.

Pros and Cons

• O – The king of gauges. There is nothing like watching an O gauge steam engine slip its drivers as it starts a long freight train. Large, heavy and realistic this gauge is expensive and requires a lot of space. If you have a big budget and plenty of room, go O.

• S – Good compromise between O and HO makes it easy to add details to trains and buildings. Not a large variety of equipment available. If you choose S you will definitely sharpen your scratchbuilding skills.

• HO – There are so many products offered in HO that the modeler can select which part of the hobby he wants to concentrate on. Ready-built structures, ready-to-run locos and cars, scenery supplies, even completely finished layouts can be obtained. The amount of detail on the abundance of various items is amazing. Does not require a large amount of space to model a well-equipped railroad.

• N – The absolute winner when it comes to the most railroad per square ft. The quality and detail of models in this small gauge have improved so greatly in recent years that it now rivals HO in popularity. If you enjoy watching long, long trains winding around a layout, N is for you. A large amount of equipment, structures, and scenery supplies are obtainable.

In addition to the gauges listed above, there are a number of modelers who specialize in narrow gauge. This is identifiable by the letter “n” attached to the gauge letter. On3, Sn3, Hon3 are typical designators for 3ft. narrow gauge, 3ft. being the distance between rails.

To use the conversion factors table, pick the scale to convert FROM across the top row.Pick the scale to convert TO down the left column.For example to convert HO measurements to O scale measurements, multiply the HO factor by 1.815 to get the O scale value.40’ HO scale boxcar =5.2”— HO 5.2” x O conv. Factor 1.815 = 9.4” O scale boxcar