Automotive Electrical & Wire Gauge Calculator

Ohm's law, watts to amps, wire size by voltage drop and fuse size estimates.

Ohm's law and power (enter any two)
Wire size by voltage drop

Notes

The wire calculation uses copper resistivity at 20 °C over the full circuit (out and back). Bundled wires, high ambient temperature and long continuous loads need a larger size. The fuse must protect the wire: choose a fuse no larger than the wire's rating, and size for about 125% of continuous load. These are estimates; follow the equipment maker's instructions.

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