Wire size
What size wire should I run?
Amps, distance, and how warm it gets in there. Out comes a gauge, the voltage at the far end, and a fuse that protects it.
How the math works
- Target wire area in circular mils =
10.75 × amps × one-way feet × 2 ÷ volts you can afford to lose. The ×2 is the trip out and back. - Ampacity comes from the published table for 105°C copper, then derated: 85% inside a hot engine bay, and 70%, 60%, 50%, or 40% when 3, 4 to 6, 7 to 24, or 25 or more wires share a bundle.
- The pick is the thinnest wire that clears both the area and the derated amps.
- Fuse: at least 125% of the load, rounded up to a standard size, and never bigger than what the wire can carry.
Same formula and constants as the calculator on the previous megawattrv.com. This is a planning tool. Have a qualified electrician check anything you wire.