Practical tools for measured work
Train Length & Siding Capacity Calculator
Scale a train's prototype length to the model, check it against your siding and find how many cars fit.
Calculate the layout, check the diagram, then print the result for the shop or jobsite.
Prototype length over the couplers.
Prototype length over the couplers.
Prototype feet. Leave at 0 if your lengths already include couplers.
Length between the clearance point and the end of the track, in model units.
The train fits the siding with the locomotives listed.
How it works
Formula: add the prototype length of every locomotive and car, plus any extra gap per vehicle, then divide by the scale ratio. Prototype feet are converted to model length at 304.8 mm per foot.
Siding capacity: the number of cars is the siding length minus the locomotives, divided by the length of one car. Use the usable length, from the clearance point to the end of the track, not the full length of the track.
Lengths: use the length of each car over the couplers. Model and prototype lengths differ, so measure your own cars if you want an exact fit.
Current-input example
The result above uses these exact values. This snapshot is included when the page is printed so the output can be checked against the original measurements.
- Measurement unit
- Inches
- Scale
- HO (1:87.1)
- Locomotives
- 2
- Locomotive length
- 70 ft
- Cars
- 10
- Average car length
- 53 ft
- Extra gap per vehicle
- 0 ft
- Usable siding length
- 96
Primary result: Train length on the layout: 92.308 in.
Before using the result
- Measure from the datum or reference edge described by this tool, and do not mix inside, outside and centerline dimensions.
- Keep inputs in the displayed units and preserve more precision than the final cutting or purchasing tolerance requires.
- When the result is close to a limit, verify it with a test piece, field measurement, manufacturer drawing or qualified project professional.
Limitations
The calculation uses average car and locomotive lengths and assumes the train stops entirely within the siding. It does not include a caboose, end-of-train device, stopping margin or coupler compression. Measure the actual train on the siding before finalising the track plan.
Frequently asked questions
Should I use model or prototype lengths?
Enter prototype feet. The tool converts them for the chosen scale and shows the model length in your unit.
Does it work for metric layouts?
Yes. Choose millimetres for the siding length. Vehicle lengths stay in prototype feet because that is how equipment lengths are usually published.
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