Model Train Calculators
Free online model train calculators.
Convert between scales, calculate track lengths, grade percentages, and layout dimensions for model railroaders.
Scale conversion, curve radius, grades, track and layout planning. 9 calculators for model railroaders. Decoder and power supply sizing overlaps with Electronics.
Minimum curve radius scales with the longest car rather than the locomotive, and the multiplier is 3 to 4 times car length for reliable running. In HO that means 18 inches handles short freight, six-axle diesels and 70-foot cars want 22, and big steam asks for 30 or more. Building to the tightest radius a manufacturer will admit to is how a layout ends up running the stock you own today and derailing everything you buy next year.
Grade punishes a model railway far harder than the percentage suggests. 2% is the practical ceiling in HO even though 4% is physically possible, because a model locomotive has no weight to borrow against the climb. A grade that looks gentle on the plan halves the train length you can pull up it.
Scale speed is worth checking too. Most layouts run at what would be well over 100 real miles per hour, which is why the trains never quite look right.
Model Train Scale Speed Calculator
Convert prototype locomotive speed to true model speed for HO, N, O, G, S, and Z scales. Shows results in mph, inches per second, and cm per second.
DCC Decoder Amperage Calculator
Pick a DCC decoder by motor stall amps and continuous draw. Get headroom advice for HO, N, O scale locos and avoid burned-out decoders from undersizing.
Model Train Minimum Curve Radius Calculator
Calculate minimum curve radius for model trains by car length and scale. Find the tightest safe radius for HO, N, O, and other scales without derailment.
Model Train Ballast Volume Calculator
Calculate ballast volume needed for model railroad track by scale, track length, and profile depth. Returns required amount in quarts, liters, and bags.
Model Train Grade/Climb Calculator
Find the horizontal run needed for a model railroad grade from your rise and target grade. Shows max grade by scale (Z, N, HO, S, O, G) and cars pulled uphill.
Model Train Layout Scenery Area Calculator
Calculate net scenery area for a model train layout by subtracting track and structures from total area. Returns square inches of groundcover and foam needed.
Model Train Power Supply Calculator
Calculate the right power supply wattage and amperage for your model train layout based on scale, locomotives, and accessories.
Model Train Scale Converter
Convert real-world dimensions to model train scale and back. Covers HO (1:87), N (1:160), O (1:48), Z (1:220), G (1:22.5), and any custom scale ratio.
Model Train Track Length Calculator
Calculate total track length for your model train layout in scale feet and real inches. Plan your loop, siding, and yard track requirements.