Yard Ladder Design Calculator

1. Select your scale from the dropdown. This sets default track spacing based on NMRA recommendations.
2. Choose the number of yard tracks you need. Remember that more tracks means a longer ladder.
3. Select your turnout frog number. #6 is the standard choice. Larger numbers create gentler angles but longer ladders.
4. Adjust track spacing if needed. Tighter spacing saves space but makes rerailing harder.
5. Choose simple or compound ladder configuration. Compound saves space but needs more turnouts.
6. Review results for ladder length, turnout count, and total track requirements.

The calculator assumes straight ladder construction with standard turnout geometry. Curved ladders require more complex calculations and are not covered here.

• Ladder length: Total distance from the first turnout to the last, measured along the lead track. This is how much linear space your ladder consumes.
• Track length differential: In a simple ladder, each successive track is shorter by approximately one turnout length. The first track off the ladder is longest; the last is shortest.
• Turnout count: Total switches needed for the ladder. Useful for budgeting since turnouts are often the most expensive track components.
• Car capacity: Approximate number of 40-foot equivalent cars each track can hold. Based on scale-specific car lengths.

Remember that the track length differential affects operations. If you need consistent capacity on every track, design based on your shortest track, not your longest.

The frog number is the single most important decision for yard ladder design. Here's what each offers:

#4 Turnouts

Steepest angle (14.5°), shortest length. Saves the most space but works best with short equipment like 40-foot cars and older steam locomotives. Modern 89-foot autoracks and long passenger cars will fight you. Equivalent to roughly an 18-inch radius curve.

#5 Turnouts

Popular middle ground at 11.4° angle. Micro Engineering's standard offering uses this size. Handles most equipment reliably and works well for space-constrained yards.

#6 Turnouts

Industry standard for reliable operation at 9.5° angle. Handles all modern equipment including 89-foot cars without complaint. Recommended minimum for backing moves where visibility is limited. Requires more space than #4 or #5.

#8 Turnouts

Gentlest angle (7.2°), longest length. Common on prototype mainlines but rarely needed in model yards. Use for high-speed diverging moves on your main, not for classification work.

Simple Ladder

Each turnout branches directly off the lead track in sequence. This is the standard approach for most model yards. It's straightforward to build, easy to wire, and simple to understand operationally. The trade-off is that each track is progressively shorter than the one before it.

Compound Ladder

A compound ladder starts with a turnout (or wye) that splits the lead into two branches. Additional turnouts then branch from each side. This design can fit more tracks in the same linear space, sometimes increasing capacity by 40-50% or more.

The trade-off is complexity. You need more turnouts, wiring is more involved, and switching moves require more thought. A 6-track simple ladder might become an 11-track compound ladder in nearly the same footprint, but you'll need roughly twice the turnouts.

For most home layouts, a simple ladder works fine. Compound ladders shine in club layouts or when you absolutely must maximize tracks in minimum space.

Yard spacing can be tighter than mainline spacing because speeds are lower and equipment is typically uncoupled. Staging yards benefit from slightly wider spacing for hand access when rerailing cars or adjusting consists.

Note that spacing is measured center-to-center. A 2-inch spacing in HO leaves only about 1.25 inches of actual clearance between car sides.

Yard tracks too short

Each track in a simple ladder is shorter than the one before it. If you need 10-car capacity on every track, design based on your shortest track, not your longest. Otherwise your last few tracks become nearly useless.

Forgetting the lead track

The lead track (the one the ladder branches from) needs to be long enough for your longest cut of cars. If your lead can only hold 5 cars but you need to switch 10-car cuts, you'll block the mainline during every switching move.

Ignoring fouling points

A car spotted too close to a turnout fouls the adjacent track. Mark fouling points clearly and subtract that length from your usable capacity calculations. A 4-foot track might only hold 3 cars if the last 10 inches are in the fouling zone.

#4 turnouts with modern equipment

Those 89-foot autoracks and articulated locomotives will derail or bind. Test your longest equipment through every route before committing to track. Better to discover the problem now than after the ballast is glued.

No runaround

Without a way to get the locomotive from one end of a cut to the other, switching becomes tedious or impossible. Make sure you have a runaround track or access from both ends.