Voltage drop calculator
How much voltage a cable run loses, and what is really left at the load. Counts both legs of the circuit, which is where most people go wrong.
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Voltage dropped in the cable
138 mV
Voltage actually at the load
11.9 V
This is the number that matters.
Loss
1.1 %
Under 3% is comfortable. Over 5% and something will misbehave.
Cable resistance (both legs)
0.138 Ω
Wasted as heat in the cable
138 mW
Copper at 20 °C. Warm wire has a little more resistance — roughly 4% more per 10 °C — so treat this as the best case.
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