Wire Gauge Calculator

If you know the max current of the appliance.

7.5A

12V11.40V

Circuit Voltage

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Voltage DropThe loss of energy as current moves through a wire results in voltage drop. A larger wire has less resistance and minimizes drop.

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Load CurrentMaximum current flow expected from the load.

Wire Length (one-way)Distance from the power source to the load. The calculator doubles this for the full round-trip wire length.

Distance from source to load

Fuse / Breaker

I don't know — tell me!I already have a fuse:

Derating FactorsFactors that reduce the wire's effective ampacity or increase the required size.

Ambient temp > 50°C (122°F) Equivalent to "In Engine Room" per ABYC standards. Reduces wire ampacity by 15%, since wires in hot areas (ceiling, walls) have less capacity to dissipate the heat generated by current flow.Load runs for more than 20min Increases the load current by 25% for voltage drop calculation (not for fuse sizing). This accounts for the extra heat that builds up when current flows continuously.Wire in conduit, insulation sleeve, or bundled with 2+ other wires Wire ampacity is reduced by 30%, since its ability to dissipate heat generated by current flow is reduced.

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Enter a load current and wire length to see results.

1. Wire size matters for safety (fire hazard) and performance (voltage drop causing intermittent issues).

2. Depends on current and length — so even if a friend used the same components, you most likely need different wire gauges.

3. Based on ABYC standards, 105°C copper wire conductor. For reference only; have your installation checked by a professional.