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Critical dimentions for scale modellers.

Critical dimentions for modellers of
British standard gauge railways
in the popular modelling scales.

Standard Dimentions.

Standard dimentions as defined by the British Railway Modelling Standards Bureau
with additions for British `N'gauge and 2mm finescale by Ozz Scott.
British N gauge, 1/148 scale.2mm Finescale, 1/152 scale.

Platforms, station buildings and bridges.

Track, platforms, buildings and bridge dimentions.

Tunnel and overbridge dimentions.

Track, tunnel and overbridge dimentions.
Standard Dimentions
Ref
Letter
See
Note
Prototype
(Feet)
N gauge
(1/148)
2mm Fine
(1/152)
TT3
(3mm)
HO
(3.5mm)
OO
(4mm)
EM
(4mm)
O fine
(7mm)
A
1
08.00
16.50
16.00
24.00
28.00
32.00
32.00
56.00
B
1
06.25
12.89
12.50
18.75
21.75
25.00
25.00
43.75
C
1
12.50
25.78
25.00
36.75
43.75
50.00
50.00
87.50
D
2
03.00
06.18
06.00
09.00
11.50
12.00
12.00
21.00
E
10.50
21.65
21.00
31.50
36.75
42.00
42.00
73.50
F
13.50
27.84
27.00
40.50
47.25
54.00
54.00
94.50
G
05.50
11.34
11.00
16.50
19.25
22.00
22.00
38.50
H
3
09.50
19.59
19.00
28.50
33.25
38.00
38.00
66.50
J
05.65
11.65
11.30
17.00
19.75
22.50
22.50
39.50
K
09.00
18.56
18.00
27.00
31.50
36.00
36.00
63.00
L
05.30
10.93
10.60
16.00
17.25
21.25
21.25
37.00
M
03.50
07.21
07.00
10.50
12.25
14.00
14.00
24.50
N
00.75
01.54
01.50
02.25
02.50
03.00
03.00
05.25
O
4
06.50
13.40
13.00
23.75
21.50
31.50
31.50
45.00
P
4 *
11.15
22.99
22.30
38.00
40.00
50.00
45.00
80.00
Q
03.50
07.21
07.00
10.50
12.25
14.00
14.00
24.50
R
1
15.00
30.93
30.00
45.00
52.50
60.00
60.00
105.00
S
5
13.00
26.81
26.00
39.00
45.50
52.00
52.00
91.00
T
5
19.50
40.21
39.00
58.50
68.25
78.00
78.00
136.50
U
5
06.75
13.92
13.50
20.25
23.75
27.00
27.00
43.75
V
1
05.33
10.99
10.66
16.00
18.50
21.25
21.25
37.25
W
6
04.71
09.00
09.42
12.00
16.50
16.50
18.00
32.00
X
1
06.00
12.37
12.00
18.00
21.00
24.00
24.00
42.00
Y
1 +
02.40
04.95
04.80
09.00
09.50
11.00
10.00
17.50
Z
1
01.00
02.06
02.00
03.00
03.50
04.00
04.00
07.00

- NOTES -

1 = Minimum dimentions.
2 = Standard (minimum for prototype 2ft 9in).
3 = Maximum dimentions.
4 = Prototype dimentions are minimum.
5 = In `N', `2mm fine' `TT-3', `OO' and `O' coarse gauges, an extra 1.8mm, 2mm, 3mm, 5mm and 7mm respectively is necessary on curves.
6 = In British N gauge, 9mm gauge track is used. The correct 1/148th scale track gauge works out at 9.7143mm. All N guage models are built to suit available 9mm gauge trackwork.
* = Dimentions are for straight running roads (Center to Center), for curves increase as above. (see 5)
+ = Dimentions are for straight platforms, increase on curves as necessary.
The track gauge (W) is measured between the inside faces of the running rails. Gauge widening may be applied to tight curves as required. (This is normally only done on hand built track)

Thanks must go to `Model Rail' magazine for publishing the BRMSB standard dimentions for `TT3', `HO', `OO', `EM' and `O fine' scales in the July 2000 issue which prompted me to add the dimentions for `British N gauge' and `2mm finescale'. The N gauge dimentions are for British 1/148th scale. The 2mm finescale dimentions are for 1/152 scale.

Copyright Notes

All content Copyright ©1999/2000 Ozz Scott unless stated otherwise.

The labelled diagrams (Fig 01 and Fig: 02) on this page were drawn by myself (Ozz Scott) and are based on the diagrams published in the July 2000 issue of Model Rail magazine.

The standard dimentions for `TT3', `HO', `OO', `EM' and `O fine' scales are those defined by the British Railway Modelling Standards Bureau.