History of HO scale


The usual standard gauge railway is 1435 mm. A model of 16.5 mm gauge accordingly corresponds to a reduction ratio of 1:87.

This ratio is referred to international model railways with H0.At the beginning of the 20th Century was the size 0th. However, it was for many a little too big and it was decided then to a smaller scale in which one simply halved the size 0 and she called H0 (Halb-Null = half zero).


First, there is the 3-wire AC system (known, for example, under Märklin), on the other hand, the 2-wire direct current system. These two systems are among themselves incompatible.

In Great Britain is used instead of H0 the size 00, both of which have a common past.

Before World War II H0 and 00 were synonymous for spacings of 16 and 16.5 mm for scales 1:72 and 1:91, regardless of manufacturer. With increasing standardization H0 was finally set at 16.5 mm gauge and scale of 1:87, while 00 remained as a term for the scale 1:76 and 16.5 mm gauge.

Worldwide prefer 80% of all model railroaders the size H0.


The European Union of Model Railroad and Railroad Fans (MOROP), sets the NEM standard. The two official languages of the MOROP are German and French.


There are 12 standardized scales.


The table should be read as follows:

- for the Model scale (orange) read diagonally from right to left

- For the model-rail gauge (purple color), please read vertically from bottom to top.


real gauges (mm) scale ratio 1:220 1:160 1:120 1:87 1:64 1:45 1:32 1:22,5 1:16 1:11 1:8 1:5,5
1250 - 1700 . Z N TT H0 S 0 I II III V VII X .
850 < 1250 Zm Nm TTm H0m Sm 0m Im IIm IIIm Vm VIIm Xm . .
650 < 850 Ne TTe H0e Se 0e Ie IIe IIIe Ve VIIe Xe . . .
400 < 650 TTi H0i Si 0i Ii IIi IIIi Vi VIIi Xi . . . .
  4,5 6,5 9 12 16,5 22,5 32 45 64 89 127 184 260  
Model gauges (mm)




The attached small letters indicate the different widths of the narrow gauge prototype.

                 e means a narrow gauge

                 m applies to narrow-gauge railway


There is also the additional letters f for Feldbahn and p for Parkbahn ridable miniature railway (real measured 381 mm).

Let's take a meter gauge, in H0 size they would have the name H0m and a track width of 12 mm.

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