Rail Sizes for

Protoypes and

Model Railroad



Information on Prototype Rails and Sizes

There are web sites with valuable information on this fascinating (or mundane) topic. Scale model railroaders are often concerned about the size of rail they are using. The railway historians among us try very hard to produce model railroads that contain rail that matches the rail used by the prototypes being represented at the matching point in history.

The quest for a perfect representation is made difficult by several factors. First, the rail in use in 1840 may be different from that in use in 1845 at the same geographic location. It is almost certainly different from the rail in use in 1945 at the same spot. So, time is an important variable.

Second, rail is and has been manufactured by different organizations to varying tolerances. So, even if rail was specified a certain way, there is no assurance that the actual rail that was used is a precise match to those specifications.

Third, the steel used to make the rail varies in its resistance to wear. The technology in use by the powered locomotives and the idler wheels on rolling stock varies in its abrasiveness. The weather and traffic density are other factors governing wear on rail. So, rail that met certain specifications when newly installed may not meet those specifications when nearly worn out and ready for replacement.

Fourth, there are differing specifications for the cross-sectional profile of rail. That means that two pieces of rail which are 6 inches tall may have different weights for a standard yard-long piece.

Rail in use by the railroads is typically referred to in the modeling press by a single number: the weight of one yard of one rail. Many of us have assumed that the factors listed above can be neglected. That is OK to a certain tolerance. However, as some of us attempt greater and greater precision in our efforts to duplicate the real world in miniature, these tolerances and small differences become significant.

Some model railroad references assume that all 90 pound rail (a one-yard long piece of rail weighs 90 pounds) is the same and should be represented by rail that is .060 inches tall in HO scale. Sadly, that assumption is not supported by historical information nor by current manufacturing practice. In the chart below, we can see that brand new, 90 pound rail in HO scale might be as short as .057 or as tall as .065, depending on cross section. That sort of variance is found in several of the common rail sizes. The variances are proportionately larger in larger scales and smaller in smaller scales.

Model railroad rail is normally specified with a “code” number. For instance, some commonly available HO track is code 100. The code number stands for the number of thousandths of an inch of rail height. So, that code 100 rail is .100 inches tall. If we knew the weight of rail to be 90, then HO rail that satisfies the requirement might be code 57, code 65 or somewhere in between. That is of course, for brand new rail. Worn 90 pound rail will be shorter (and no longer weigh 90 pounds per yard).

The following links provide some additional, detailed information and some convenient compromises.

urbaneagle...RRrailsizes
pearcedale...track
harmersteel...railsections
nmra.org...rp-15_1
Comprehensive, World-Wide Rail Specs and S-Scale Conversions
S-Scale Glossary

The table on the Harmer Steel site listed above, contains information about rails. It shows information about differing cross sections for rail with nominally the same weight per yard in US pounds. The following table is based on the rail that is currently available from Harmer Steel. These folks produce railroad rail for lots of railroads. They offer rail that matches existing track.

Row Nominal
Weight
per Yard
Height Z-Scale N-Scale TT-Scale HO-Scale OO-Scale S-Scale O-Scale
1 12 2 0.009 0.013 0.017 0.023 0.026 0.031 0.042
2 16 2.375 0.011 0.015 0.020 0.027 0.031 0.037 0.049
3 20 2.625 0.012 0.016 0.022 0.030 0.035 0.041 0.055
4 25 2.75 0.013 0.017 0.023 0.032 0.036 0.043 0.057
5 30 3.125 0.014 0.020 0.026 0.036 0.041 0.049 0.065
6 35 3.3125 0.015 0.021 0.028 0.038 0.044 0.052 0.069
7 40 3.5 0.016 0.022 0.029 0.040 0.046 0.055 0.073
8 45 3.6875 0.017 0.023 0.031 0.042 0.049 0.058 0.077
9 50 3.875 0.018 0.024 0.032 0.044 0.051 0.061 0.081
10 55 4.0625 0.018 0.025 0.034 0.047 0.053 0.063 0.085
11 56 4 0.018 0.025 0.033 0.046 0.053 0.063 0.083
12   4.25 0.019 0.027 0.035 0.049 0.056 0.066 0.089
13 60 4.25 0.019 0.027 0.035 0.049 0.056 0.066 0.089
14   4.5 0.020 0.028 0.038 0.052 0.059 0.070 0.094
15   4.25 0.019 0.027 0.035 0.049 0.056 0.066 0.089
16 65 4.4375 0.020 0.028 0.037 0.051 0.058 0.069 0.092
17 70 4.625 0.021 0.029 0.039 0.053 0.061 0.072 0.096
18 72 4.75 0.022 0.030 0.040 0.055 0.063 0.074 0.099
19 75 4.8125 0.022 0.030 0.040 0.055 0.063 0.075 0.100
20   4.75 0.022 0.030 0.040 0.055 0.063 0.074 0.099
21   4.9375 0.022 0.031 0.041 0.057 0.065 0.077 0.103
22   5 0.023 0.031 0.042 0.057 0.066 0.078 0.104
23   4.9375 0.022 0.031 0.041 0.057 0.065 0.077 0.103
24 80 5 0.023 0.031 0.042 0.057 0.066 0.078 0.104
25   5.125 0.023 0.032 0.043 0.059 0.067 0.080 0.107
26 85 5.1875 0.024 0.032 0.043 0.060 0.068 0.081 0.108
27   5.125 0.023 0.032 0.043 0.059 0.067 0.080 0.107
28   5.1875 0.024 0.032 0.043 0.060 0.068 0.081 0.108
29   5 0.023 0.031 0.042 0.057 0.066 0.078 0.104
30   5.21875 0.024 0.033 .043 0.060 0.069 0.082 0.109
31   5.125 0.023 0.032 0.043 0.059 0.067 0.080 0.107
32   5 0.023 0.031 0.042 0.057 0.066 0.078 0.104
33   5.375 0.024 0.034 0.045 0.062 0.071 0.084 0.112
34 90 5.375 0.024 0.034 0.045 0.062 0.071 0.084 0.112
35   5.625 0.026 0.035 0.047 0.065 0.074 0.088 0.117
36   5.265625 0.024 0.033 0.044 0.060 0.069 0.082 0.110
37   5.625 0.026 0.035 0.047 0.065 0.074 0.088 0.117
38   5.53125 0.025 0.035 0.046 0.064 0.073 0.086 0.115
39   5.5 0.025 0.034 0.046 0.063 0.072 0.086 0.115
40   5.375 0.024 0.034 0.045 0.062 0.071 0.084 0.112
41   5 0.023 0.031 0.042 0.057 0.066 0.078 0.104
42 100 5.75 0.026 0.036 0.048 0.066 0.076 0.090 0.120
43   5.6875 0.026 0.036 0.047 0.065 0.075 0.089 0.118
44   5.5 0.025 0.034 0.046 0.063 0.072 0.086 0.115
45   6 0.027 0.038 0.050 0.069 0.079 0.094 0.125
46   5.640625 0.026 0.035 0.047 0.065 0.074 0.088 0.118
47   6 0.027 0.038 0.050 0.069 0.079 0.094 0.125
48   5.703125 0.026 0.036 0.048 0.065 0.075 0.089 0.119
49   5.75 0.026 0.036 0.048 0.066 0.076 0.090 0.120
50   5.75 0.026 0.036 0.048 0.066 0.076 0.090 0.120
51   6 0.027 0.038 0.050 0.069 0.079 0.094 0.125
52   5.625 0.026 0.035 0.047 0.065 0.074 0.088 0.117
53 101 5.4375 0.025 0.034 0.045 0.062 0.072 0.085 0.113
54 105 6 0.027 0.038 0.050 0.069 0.079 0.094 0.125
55   6 0.027 0.038 0.050 0.069 0.079 0.094 0.125
56 110 6.75 0.031 0.042 0.056 0.077 0.089 0.105 0.141
57   6.5 0.030 0.041 0.054 0.075 0.086 0.102 0.135
58   6 0.027 0.038 0.050 0.069 0.079 0.094 0.125
59 112 6.625 0.030 0.041 0.055 0.076 0.087 0.104 0.138
60   6.75 0.031 0.042 0.056 0.077 0.089 0.105 0.141
61 113 6.8125 0.031 0.043 0.057 0.078 0.090 0.106 0.142
62 115 6.625 0.030 0.041 0.055 0.076 0.087 0.104 0.138
63   6.5 0.030 0.041 0.054 0.075 0.086 0.102 0.135
64 119 6.8125 0.031 0.043 0.057 0.078 0.090 0.106 0.142
65 122 6.78125 0.031 0.042 0.057 0.078 0.089 0.106 0.141
66 127 7 0.032 0.044 0.058 0.080 0.092 0.109 0.146
67 130 6.625 0.030 0.041 0.055 0.076 0.087 0.104 0.138
68   6.75 0.031 0.042 0.056 0.077 0.089 0.105 0.141
69 131 7.125 0.032 0.045 0.059 0.082 0.094 0.111 0.148
70 132 7.125 0.032 0.045 0.059 0.082 0.094 0.111 0.148
71 133 7.0625 0.032 0.044 0.059 0.081 0.093 0.110 0.147
72 136 7.3125 0.033 0.046 0.061 0.084 0.096 0.114 0.152
73 140 7.3125 0.033 0.046 0.061 0.084 0.096 0.114 0.152
74 152 8 0.036 0.050 0.067 0.092 0.105 0.125 0.167
75 155 8 0.036 0.050 0.067 0.092 0.105 0.125 0.167


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