Free online calculator

Wire voltage drop calculator

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Example Vdrop = 420 mV — power loss = 840 mW (R = 210 mΩ) — 3.5% of 12 V

$V_{\mathrm{drop}}=I\times R_{\mathrm{wire}}$, where $R_{\mathrm{wire}}=(\Omega /m)\times \mathrm{length}\times 2$ for a round trip. The ohms per metre come from the AWG table.