Märklin C track or Märklin K track: the differences side by side

Benjamin | TrackDrawer.com · published 29 October 2026

The biggest difference: Märklin C track has a fixed roadbed 40 mm wide, while Märklin K track sits on its sleepers without a roadbed and is 32 mm wide. On top of that, K tracks lie closer together (64.6 versus 77.5 mm), K has a tighter smallest curve and a flexible track, and C has neither. Both are three-rail AC with a centre conductor, so your trains run on either.

What they have in common

C track and K track are two Märklin track systems for H0 scale, gauge 16.5 mm. Both use three-rail AC: current comes in through a row of stud contacts along the middle of the track (the centre conductor) and returns through the two running rails. A locomotive with a pickup skate runs on both systems without changes.

The range is built up in a similar way too: straights in several lengths, curves in five common radii, left and right turnouts, curved turnouts, a three-way turnout, crossings and double slips. The difference lies in the dimensions and in the way you lay them.

The differences in one table

Roadbed or no roadbed

This is the difference you see at once, and it shapes everything else. C track has a plastic roadbed with sleepers and ballast moulded in. The pieces click firmly together and stay put on the floor or a carpet without being screwed down. The roadbed also hides the wiring and, on turnouts, the motor.

K track has no roadbed: rails on a grid of sleepers. It only looks its best once you fix it to a baseboard, often on cork underlay, and ballast it yourself. That takes more work, but you decide how the layout looks.

Seen from above, K track takes less room: 32 mm against 40 mm. Next to the radii and the track spacing that is small, but it counts at every edge of the board.

Curve radii and space

With the Industriekreis of 295.4 mm, K track has a tighter curve than anything C track offers. The name says it: that curve is meant for tight industrial sidings and small locomotives, not for long coaches. Check the minimum radius the manufacturer gives for your stock.

You see that difference in the measurements with the TrackDrawer Auto-designer (typical stock, 5 cm edge all round). A closed loop of K track fits on 75 x 75 cm, as an oval on the Industriekreis. For C track it is 90 x 90 cm, as a circle of twelve R1 curves. How much space C track needs for other shapes is in how much space you need for C track.

For a loop with a passing track, too, K track needs less board. At 75 cm deep the designer found the first K track variant from 140 cm wide ("Station with two platforms on Industriekreis, plus 2 sidings", 28 pieces, 4.64 m of track); at 85 cm deep it stays at 140 cm. With C track it works from 160 cm wide at 90 cm deep. K track therefore saves 20 cm in width and 15 cm in depth, provided your stock can handle the Industriekreis.

Normalkreis I of K track and R1 of C track share the same radius: 360 mm. Above that the series diverge, because each follows its own track spacing.

Track spacing

On C track two parallel tracks lie 77.5 mm apart, on K track 64.6 mm. You can see it in the radii: 437.5 minus 360 is 77.5, and 424.6 minus 360 is 64.6. The turnout and reverse curve are matched to that spacing, so a passing loop automatically sits at the right distance. With K track, stations end up a little more compact in width. More on this in track spacing: how far apart do two tracks lie.

Turnouts and the turnout pattern

Both systems follow the same pattern: after the turnout a reverse curve brings the diverging track parallel again, and a compensation piece on the straight side keeps both tracks the same length. The dimensions differ. The C turnout is 188.3 mm long and diverges on R2 over 24.3 degrees. The K turnout is 168.9 mm long and diverges on 424.6 mm over 22.5 degrees.

For smoother running both have a slim turnout: 12.1 degrees on C, 14 degrees 26 minutes on K. A curved turnout, for a passing loop in the curve, exists in both systems.

Flexible track: K only

In our catalogue K track has a flexible track (2205, 900 mm), C track does not. With flexible track you bend a curve of any radius yourself and lay long, flowing transitions where no fixed piece fits. That suits a permanent layout where the track is fixed down. With C track you work with fixed pieces only, which makes planning predictable.

K also has more short straights (from 22.5 mm), handy for closing a gap. The shortest C straight is 64.3 mm. C does have an end piece with buffer stop as a track piece (24977).

Mixing with the transition track

You do not have to choose for life. The transition track 24922 (180 mm) connects C track to K track. That way you can combine, for example, a fiddle yard or a permanent section in K track with a visible part in C track, or connect an old box of K track to a new starter set. If you have inherited such a box, read giving your old box of track a second life.

When do you choose which?

• Floor, carpet, quick set-up and take-down: C track. The roadbed holds the pieces together and the line is stable straight away, without a baseboard.
• Permanent layout with your own ballast and scenery: K track. You fix the track down, choose your own underlay and look, and can lay free shapes with flexible track.
• Little depth, small stock: K track with the Industriekreis fits a loop on a smaller board, also with a passing loop.
• Wider fixed radii and predictable pieces: C track, with R1 to R5 and a fixed track spacing of 77.5 mm.

Whichever you choose, both systems run the same trains.

Your plan with either system

In TrackDrawer you pick C track or K track as the system, enter your own stock and let the Auto-designer lay out a plan that fits your baseboard. The designer checks that the line closes, that nothing collides and that tracks sit at the correct track spacing.