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Wire Gauge Voltage Drop Calculator

Calculate round-trip voltage drop, drop percentage, and power loss for a given wire gauge, cable run length, and current � essential for automotive, solar, and low-voltage DC systems.

Resistance values in mO/m at 20�C. Resistance increases ~0.4% per �C.

Results

Total Voltage Drop (round trip)0.656 V drop
Voltage Drop %5.47%
Power Loss in Wire6.56 W

📖What is it?

Voltage drop in a wire depends on current, wire length, and resistance per unit length: V_drop = 2 � L � I � R_per_m. The factor of 2 accounts for the round trip (positive and negative conductors). For 12V DC systems, a drop >3% (0.36V) is considered excessive. Power lost in the wire = V_drop � I (in watts).

🎯How to use

Select the wire gauge, enter the one-way cable run length, current, and supply voltage. The total round-trip voltage drop, percentage, and power loss are computed. If the drop percentage exceeds 3%, go up one or two wire gauges.

💡Example scenario

14 AWG, 5m one-way, 10A, 12V system: R = 6.56 mO/m. V_drop = 2 � 5 � 10 � 0.00656 = 0.656 V. Drop% = 0.656/12 � 100 = 5.5% � excessive! Switch to 10 AWG (3.28 mO/m): V_drop = 2 � 5 � 10 � 0.00328 = 0.328 V ? 2.7% � acceptable.

🏆Pro tip

For solar panel installations, keep voltage drop <1% for maximum harvest efficiency. Use a wire sizing calculator specific to your NEC/IEC jurisdiction for safety compliance. At high temperatures (engine bay, attics), wire resistance increases and current capacity decreases � derate accordingly. Crimp connections and fuse holders also add resistance; use high-quality tinned connectors.