DC Wire Gauge Calculator
Find the right wire gauge for your DC circuit.
DC Wire Gauge Calculator
Find the right wire gauge for your DC circuit
Formula
cmil = 2 × L × ρ × I / V_dropHow to Use
- 1Enter current (amps) — Input the maximum current your circuit will carry.
- 2Enter wire length — Measure the one-way wire run distance in feet.
- 3Set acceptable voltage drop — Choose maximum voltage drop — typically 3% for power lines, 5% for lighting.
- 4Get recommended gauge — See the minimum AWG wire gauge to keep voltage drop within limits.
Frequently Asked Questions
What voltage drop is acceptable for solar?
3% maximum for main power runs (panels to controller, controller to batteries). Up to 5% for branch circuits and lighting.
Why is wire gauge important for DC?
DC systems run at lower voltages than AC, so the same wattage requires more current. Higher current needs thicker wire to avoid dangerous overheating.
What AWG for 30 amps at 12V?
For a 10-foot run at 3% drop: 6 AWG. For longer runs, you need even thicker wire. Always check with this calculator for your exact setup.
Can I use AC wire for DC circuits?
Yes, standard copper THHN/THWN wire works for DC. The gauge requirements are calculated the same way based on current and distance.