Automotive Wire Gauge Calculator
Find a recommended copper wire size for LED light bars, auxiliary lights, and 12V automotive accessories.
Enter your installation details
Distance from power source to accessory, 3–60 feet
Choose the voltage expected during operation
Use the total running current for all connected accessories
Recommended wire size
How the calculation works
The calculator uses a 4% maximum voltage-drop target to approximate the original SMD 13.8V chart. It calculates current from watts ÷ volts when watts are selected, then estimates voltage drop using copper conductor resistance and a complete supply-and-return circuit.
Formula: Voltage drop = 2 × one-way length (ft) × current (A) × copper resistance (ohms/ft). The recommended AWG is the smallest listed wire that meets the voltage-drop target and a conservative general-purpose current-capacity screening limit.
Available wire sizes: 18, 16, 14, 12, 10, 8, 6, 4, 2, 1, 1/0, 2/0 and 4/0 AWG. Results are estimates at approximately 20°C; resistance rises as the wire gets hot. For long runs, heavy loads, or critical circuits, have the installation checked by a qualified professional.
