A track plan for Märklin C track: radii, turnouts and spacing
Benjamin | TrackDrawer.com · published 13 November 2026
A track plan for Märklin C track rests on three numbers: 30 degree curves, twelve of which make a circle, a standard turnout that branches off at 24.3 degrees on radius R2, and a track spacing of 77.5 mm. Once you know those three dimensions and the matching filler pieces, you draw plans that really close on the baseboard. Below are all the values from the catalogue, with the combinations you need most often while planning.
How much space a C track layout takes is covered in a separate article: How much space do you need for a Märklin C track layout? This one is about the geometry: which pieces fit together.
The basic grid: 30 degrees and 360 mm
Almost everything in Märklin C track follows from two dimensions. The first is the 30 degree curve: twelve make a full circle, six a half circle, three a quarter. The second is the length of 360 mm. That is at once the length of the long straight 24360, the radius R1, and the sum of the two most common straights: 24188 (188.3 mm) plus 24172 (171.7 mm).
That is no accident. The standard turnout is 188.3 mm long. Add 24172 behind it and the through track is back at exactly 360 mm, on the same grid as the rest of the layout. That is why 24188 and 24172 almost always come in pairs in starter sets and extension sets.
The roadbed is 40 mm wide seen from above. It counts in the plan: the outer edge of a track lies 20 mm from its centre line.
The radii and the gaps between them
C track has five standard radii, measured to the centre line of the track.
| Radius | Size | Gap to the previous one | 30 degree curve | Other curves | Circle outside the roadbed |
|---|---|---|---|---|---|
| R1 | 360 mm | 24130 | 24115 (15°), 24107 (7.5°) | 760 mm | |
| R2 | 437.5 mm | 77.5 mm | 24230 | 24215 (15°), 24207 (7.5°), 24206 (5.7°), 24224 (24.3°) | 915 mm |
| R3 | 515 mm | 77.5 mm | 24330 | 24315 (15°) | 1070 mm |
| R4 | 579.3 mm | 64.3 mm | 24430 | 1198.6 mm | |
| R5 | 643.6 mm | 64.3 mm | 24530 | 1327.2 mm |
The gap column is the one to watch. R1, R2 and R3 are each 77.5 mm apart, exactly the normal track spacing. A pair of R1 and R2, or R2 and R3, therefore forms a double-track curve that joins a double-track straight without a kink. R4 and R5 are only 64.3 mm apart. That dimension belongs to the tighter spacing of the slim turnouts and does not match the spacing of the standard turnout. More in Track spacing: how far apart do two tracks lie?
The standard turnout and its partners
Turnouts 24611 (left) and 24612 (right) are the workhorses of the system. The straight road is 188.3 mm long, the diverging road is an R2 curve of 24.3 degrees. Worked out, the diverging road ends 180 mm along and 38.8 mm to the side of the through track. Three partners cover most situations:
| Combination | Result |
|---|---|
| Turnout + straight 24172 on the through track | straight track of 360 mm |
| Turnout + counter curve 24224 on the diverging road | parallel track at 77.5 mm, after 360 mm |
| Turnout + curve 24206 (5.7°) on the diverging road | 30 degrees together on R2, like a 24230 curve |
| two turnouts facing each other, each with 24224 | passing loop, 360 mm long at each end |
The second row matters most. Turnout and counter curve shift the track by exactly one track spacing, and both tracks are 360 mm long afterwards. A passing loop therefore needs 360 mm at each end; with two ends that is at least 72 cm of straight before a single train stands in the loop.
The third row lets you place a turnout in an R2 curve. You replace one 24230 curve with the turnout, add 24206 to the diverging road, and the diverging road carries on around the circle while the straight road leaves along the tangent. That way a branch starts in the middle of a curve without recalculating the circle.
Slim turnouts, crossings and curved turnouts
Besides the standard turnout, the catalogue has a second family with a shallower angle:
- Slim turnouts 24711 and 24712: straight road 236.1 mm, diverging road on a 1114.6 mm radius (R9) over 12.1 degrees. According to the catalogue the diverging side needs two 24071 straights (70.8 mm). The matching counter curve is 24912 (R9, 12.1 degrees).
- Slim crossing 24740 and slim double slip 24720: both 12.1 degrees and 236.1 mm long.
- Crossing 24640 and double slip 24624: 24.3 degrees, 188.3 mm, matching the standard turnout.
- Crossing 24649: 48.6 degrees, 103.3 mm.
- Three-way turnout 24630: branches left and right, each like the standard turnout.
There is no 90 degree crossing in C track. If you plan a figure eight, you cross with 24649 or take one track over a bridge.
For a passing loop in a curve there are the curved turnouts 24671 and 24672 (R1 to R2) and the slim curved turnouts 24771 and 24772 (R3 to R4). How to use them is explained in Märklin C Track curved turnouts.
Straights as fillers
Not every gap is a multiple of 188.3 mm. For that the system has a series of short straights: 24064 (64.3 mm), 24071 (70.8 mm), 24077 (77.5 mm) and 24094 (94.2 mm), plus the longer 24229 (229.3 mm) and 24236 (236.1 mm). Two are easy to remember: 24077 is exactly one normal track spacing, 24064 exactly one tight spacing.
Some straights have a job. Feeder track 24088 is as long as 24188 and powers the layout. Switch track 24994, contact track 24995 and uncoupler track 24997 are 94.2 mm long, and there are the curved switch tracks 24194 (R1) and 24294 (R2) at 15 degrees. You end a siding with buffer stop 24977, or 24978 with a light. For the transition to older track there are 24922 to K track and 24951 to M track.
Common planning mistakes with C track
- Forgetting the filler. A turnout in a curve without 24206 leaves a 5.7 degree gap. A turnout on the through track without 24172 shifts everything after it by 171.7 mm.
- R3 and R4 as a double-track curve. They are only 64.3 mm apart. With a passing loop made of standard turnouts at 77.5 mm, that does not fit.
- A passing loop that is too short. Two times 360 mm for the turnout ends is fixed. The usable part only starts in between.
- Overlooking the roadbed. With 40 mm of roadbed an R1 circle measures 760 mm outside, not 720 mm.
Frequently asked questions
Which radius should I use for the outer circle?
For two tracks all the way round, the pair R1 and R2 or R2 and R3 fits, because they sit at the normal track spacing of 77.5 mm. R2 has the added advantage that the standard turnout branches off on the same radius.
Can I mix K track with C track?
Yes, with transition track 24922. The geometry of the two systems differs, though, so plan each part with the dimensions of its own system. The differences are set out in the comparison of C track and K track.
Plan it yourself
TrackDrawer knows every one of these pieces with its catalogue dimensions, shows the geometry grid of C track and, if you want, adds a 180 and 360 mm grid to the PDF. For ideas at different baseboard sizes, browse the C track plans in the Railfolio. Then enter your stock and let the Auto-designer lay out a plan that closes with exactly these dimensions.
