Marine Wire Sizing
Correct wire gauge ensures adequate current capacity and acceptable voltage drop. Sizing depends on load current, run length, and max drop percentage. See our electrical systems on boats for the full design guide.
Inputs for sizing
You need: load current (A), one-way length (m), system voltage (12V/24V), and max voltage drop (%). For critical circuits, use 3%. ABYC E-11 and SAE J1128 provide resistance values. Use our AWG sizing calculator to find minimum gauge.
Marine wire requirements
Tinned copper, stranded, and rated for damp locations. Avoid automotive primary wire in bilge areas. Bundle derating applies when multiple conductors share a run — consult ampacity tables for bundled installations.
Integration with other tools
Wire gauge determines ampacity; the fuse must protect the wire. After sizing, verify calculate voltage drop and fuse sizing calculator. For battery-dependent loads, check battery runtime calculator.