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Marine Cable Size Calculator — DC Voltage Drop

Voltage drop is what kills DC circuits on boats. Size any run properly: drop first, ampacity checked, fuse suggested.

Size a DC cable run properly

Voltage drop is what kills DC circuits on boats — we size for drop first, then check the cable can carry the current.

Panel to the load along the actual cable path — we double it for the return leg.

Your cable spec

Sized on copper resistivity over the round-trip run, then checked against continuous ampacity for tinned marine cable. Guidance for planning — confirm against ABYC E-11 / ISO 13297 for your installation, keep connections crimped and adhesive-heatshrunk, and fuse at the source of power, always.

Get the right cable, cut to length
BEP tinned marine cable, sold per metre — battery cable for the heavy runs, switchboard wire for the small stuff, Lloyd's-approved flex where class matters.
BEP battery cable All cable & wire
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