H0 track spacing

Recommendations for track spacing on H0 model railways

On the open line, two parallel H0 tracks are at least 46 mm apart. In a station the minimum is 52 mm. Measure from track centre to track centre. On a curve the spacing grows: the tighter the radius and the longer the coach, the further apart the tracks must sit, or the bodies will touch.

Source: NEM 112, 2016 edition. The 2024 edition gives the same values for straight track. Measured from track centre to track centre.

Left, the track bed from above. Right, the same position as a drawing. The long arrow measures 46 mm from centre to centre. The shorter arrow between the tracks measures the clear gap of 29.5 mm between the facing rails. 29.5 mm is 46 mm minus the gauge of 16.5 mm.

Three measurements that get mixed up

• Track spacing: centre to centre. That is the value in NEM 112.
• Rail spacing: in search queries this usually means the same thing. It is not the distance between the two rails of one track.
• Gauge: inside one track. For H0 that is 16.5 mm under NEM 110.
• Clear gap: track spacing minus 16.5 mm. At 46 mm, 29.5 mm remain between the facing rails. At 52 mm, 35.5 mm remain.

Why a curve needs more space

On a curve the coach ends swing outward and the middle swings inward. Two trains on a tight radius can touch even though the same tracks were clear on the straight. The spacing therefore depends on coach length, not only on the radius.

The standard splits coaches into three groups. What counts is the body length of the prototype, under NEM 103. For H0 these are the model lengths:

Group	Prototype, body up to	Bogie pivot distance up to	H0 model up to	What that means in practice
A	20.0 m	14.0 m	230 mm	Short goods and passenger coaches
B	24.2 m	17.2 m	278 mm	Medium bogie coaches
C	27.2 m	19.5 m	313 mm	Long passenger coaches

Shortened H0 models at a length scale of 1:100 that would fall into group C on the prototype may be treated as group B where the standard allows it. Do not go below the group A value even if you run no bogie stock. The larger spacing must already be fully in place at the start of the curve.

NEM 111 also limits the radius. For H0 with close couplers the smallest curve is group A 354.75 mm (21.5 times 16.5 mm), group B 412.5 mm, group C 495 mm. Below those radii the NEM 112 figures are only meant for interpolation and are not listed here.

Minimum spacing on an H0 curve

The table gives the minimum distance from track centre to track centre, in millimetres. The radius is that of the inner track. Short group A coaches need less space on the same curve than long group C coaches. From an inner radius of 1200 mm upwards, all three groups stay at the 46 mm of the open line. If your radius falls between two rows, use the value from the tighter row.

Inner radius	Group A, up to 230 mm	Group B, up to 278 mm	Group C, up to 313 mm
500 mm	50	55	59
600 mm	48	52	55
700 mm	46	50	52
800 mm	46	48	50
900 mm	46	47	48
1000 mm	46	46	47
1200 mm and above	46	46	46

Use the column of your longest coach. At a 600 mm radius, 52 mm is enough for group A, not for group C. There the minimum is 55 mm.

Close or wide

	Close to 46 mm	52 mm and more
Space	More tracks on the same area	A wider layout, less usable length
Running	Critical with long coaches and tight radii	Bodies and steps stay clear
Look	Convincing only on large radii	Calmer and easier to reach in a station
Rework	Every curve has to be measured again	More room for fingers and later scenery

Laying flex track in parallel

1. Lay the first track. Check the gauge of that one track, not the distance to its neighbour.
2. Set the spacer to the standard value: 46 mm on the open line, 52 mm in a station, and the table value on a curve.
3. The H0 scale on the tool starts at 40 mm and ends at 64.6 mm. 40 mm is below the standard. Do not use the smallest mark just because it is there.
4. Clamp rail and sleeper while you solder. The spacer sets the distance. The clamp holds the rail.
5. On a radius use two spacers per section. Otherwise the outer track wanders. The larger spacing is already there at the start of the curve.
6. After soldering, measure centre to centre and the clear gap once more, before you ballast.

What you need in your hand

The same steps, collected: Laying flex tracks and Model tracks.

Typical mistakes

• Measuring rail head to rail head and comparing that with 46 mm. The standard means the centres.
• Carrying the straight-track value all the way through the curve.
• Widening only in the middle of the curve. Coaches still clip at the transition.
• Setting the spacer to 40 mm because that is the smallest H0 mark.
• Using the track gauge as a gauge for the distance between two tracks.

Common questions

What track spacing applies to H0 on straight track?

On the open line at least 46 mm from centre to centre, in a station at least 52 mm. These are lower limits. If you have platforms, signals or long coaches, stay at 52 mm or go wider.

How do I measure H0 track spacing correctly?

Measure from track centre to track centre. The clear gap between the facing rails is smaller by the gauge, so by 16.5 mm in H0. 46 mm centre to centre becomes 29.5 mm between the rails. If you measure only the rail heads and compare that with 46 mm, you lay the tracks too far apart.

What spacing do I need on an H0 curve with a 600 mm radius?

For group A coaches, body up to about 230 mm, it is 48 mm. For group B 52 mm, for group C 55 mm. The larger value must already stand at the start of the curve. Two spacers per section keep the outer track where you put it.

Can I set the spacer to 40 mm?

The scale on the tool allows it for H0. The standard does not. 40 mm is 6 mm under the open line and 12 mm under a station. Set the spacer to 46 mm, 52 mm or the table value for the curve. The upper mark of 64.6 mm also covers wide station tracks.

What do track clamps do, and what does the track gauge check?

The track clamps hold rail and sleeper while you solder. They do not set the distance between two tracks. The track gauge for H0 checks the 16.5 mm inside one track. Only the spacer sets the distance to the neighbouring track.