Model Railway Wiring Calculator — Bus Wire & Droppers
Calculate bus wire length, dropper count, dropper wire and power supply sizing for your model railway layout.
Total track run length in metres
Number of independent power sections
Distance between dropper connections
Select an option for bus wire gauge
How We Calculate This
This calculator estimates wiring requirements based on layout length, dropper spacing and power district count.
The formula
Bus wire = Layout length x 2 wires x Districts x (1 + Extra %)
Droppers = (Layout length / Spacing) x 2 rails
Power supply = Max locos x Amps per loco x Districts
Frequently Asked Questions
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Last updated: March 2026
All calculations are estimates. Always verify quantities before purchasing materials.