Track planning
Layout Space Chart
Quick answer
A 4x8 ft sheet of plywood supports about 22 in of maximum curve radius, using half the 48 in width minus a 2 in edge margin. A 5x9 ft benchwork gives 28 in, a hollow core door gives only 13 in, and a 6x10 ft room-sized layout gives 34 in of maximum radius.
Maximum curve radius is not a matter of taste, it is arithmetic dictated by the width of the benchwork: half the width, minus a margin at each edge so the curve does not run off the plywood or into the aisle. That single formula, run for six common benchwork sizes below, answers the most basic layout-planning question before a single piece of track is bought. The track plan size calculator applies the same formula to a custom benchwork size.
What maximum radius and area does each common benchwork size support?
Maximum radius = (width in inches / 2) minus a 2 in edge margin. A 4x8 ft sheet is 48 in wide, so 48 / 2 = 24, minus 2 in margin, equals 22 in.
A 6x10 ft layout supports 34 in of maximum radius, more than double the 13 in a hollow core door allows.
| Benchwork size | Dimensions (in) | Max radius | Area |
|---|---|---|---|
| Hollow core door | 30 x 80 in | 13 in | 16.7 sq ft |
| 2x8 ft shelf | 24 x 96 in | 10 in | 16 sq ft |
| 4x8 ft sheet | 48 x 96 in | 22 in | 32 sq ft |
| 5x9 ft | 60 x 108 in | 28 in | 45 sq ft |
| 6x10 ft | 72 x 120 in | 34 in | 60 sq ft |
Max radius = width / 2, minus a 2 in edge margin. Width is the shorter dimension of the benchwork, the one the curve has to fit inside.
Is a 4x8 ft layout big enough for realistic curves?
22 in of maximum radius supports a conventional curve for most HO cars up to about 60 to 65 ft in prototype length, using the multiplier math on the minimum radius chart. It does not comfortably support conventional-radius curves for 85 ft passenger equipment, which wants roughly 35 in. A 4x8 can still run passenger equipment at the sharp end of the multiplier range, with the visible compromise of tighter overhangs and a higher derailment risk on the curve, or by keeping passenger equipment to a mostly-straight point-to-point design that avoids full-radius ovals altogether.
How much aisle space should I leave around the benchwork?
A comfortable reach across benchwork for scenery and maintenance work is about 30 in from the front edge; beyond that, reaching the back of the layout without walking around it gets difficult. Allow roughly 2 ft of aisle width per side the layout needs to be accessed from, more where the room also has to function as a walkway or double as storage. A shelf layout like the 2x8 ft example above trades maximum radius for a narrower footprint specifically to fit a tighter aisle allowance in a smaller room.
What benchwork size should a first layout actually use?
A hollow core door or a 2x8 ft shelf keeps cost and space commitment low while a beginner works out whether the hobby is a long-term interest, at the cost of a tighter maximum radius that limits which equipment runs comfortably. A 4x8 ft sheet is the traditional first "real" layout size, wide enough for a workable oval and a small yard without requiring a dedicated room. Reference published track plans sized to these exact footprints, such as 101 Track Plans for Model Railroaders or 21 Great Track Plans for Compact Layouts, rather than designing a first track plan from a blank sheet.
Sources
- Benchwork width to maximum radius formula, width / 2 minus a 2 in edge margin
Frequently asked questions
How is maximum curve radius calculated for a given benchwork size?
Take the shorter dimension of the benchwork in inches, divide by two, then subtract a 2 in margin for the edge. A 48 in wide sheet gives 48 / 2 = 24, minus 2 in, for a 22 in maximum radius. The longer dimension of the benchwork does not factor into this calculation directly, only the width the curve has to fit inside.
Why subtract a 2 inch margin instead of using the full half-width as the radius?
A curve drawn at exactly half the width would place the outer rail right at the physical edge of the benchwork, leaving no room for roadbed, scenery, a backdrop, or simple manufacturing tolerance in how the benchwork was actually built. The 2 in margin is a practical buffer that keeps the curve safely inside the usable surface.
Can I get a bigger maximum radius without a bigger footprint?
Only by changing the shape of the benchwork so its width, not its overall area, increases. An L-shaped or around-the-walls layout can support a wider practical curve in one section than the same square footage arranged as a single rectangular table, because the constraining dimension in the formula is width, not total area.
Does a 2x8 ft shelf layout support any curves at all?
Yes, about 10 in of maximum radius, which is workable for N scale short equipment and very short HO equipment but tight for most HO rolling stock. Shelf layouts at this width are more often built as point-to-point or around-the-walls designs that use the length of the shelf rather than relying on a tight oval at one end.
How much bigger does a layout need to be to run 85 foot passenger cars comfortably?
An 85 ft HO passenger car wants roughly 35 in of conventional radius, which this chart's formula needs a benchwork width of about 74 in, roughly 6 ft, to support. A 6x10 ft layout at 34 in maximum radius sits right at the edge of that requirement; anything narrower needs the sharp end of the multiplier range or a different track plan shape.
Should aisle space be subtracted from the room size before picking a benchwork footprint?
Yes. The benchwork dimensions in this chart are the layout surface itself, not the room. A room needs the benchwork footprint plus roughly 2 ft of aisle on every side that requires access, so a 4x8 ft layout realistically needs a room noticeably larger than 4x8 ft once aisles on the accessible sides are included.
Researched, not professional advice. This page is compiled from published manufacturer specifications, instruction manuals, published NMRA standards and recommended practices, and owner-review consensus, not hands-on testing. Figures described as a rule of thumb are hobby convention rather than a standard, and they are labelled that way wherever they appear. Always check a radius, a clearance or a grade against your own equipment before you cut wood or lay rail, because manufacturers vary and so does what your specific models will tolerate. Any permanent mains wiring in a layout room is work for a licensed electrician to your local code.