Wire Gauge Calculator

Type the current your project draws and how far the wire runs. Out comes the gauge that carries it without complaint.

Current

One-way run length

System voltage

Two limits, not one

A wire fails you two ways. Too thin for the current and it heats up: that's the ampacity limit, and it depends only on the gauge. Too thin for the distance and your 12 V arrives as 10.8: that's voltage drop, and it grows with every meter of copper, out and back. This calculator checks both and reports the round-trip drop for your run.

Reading the answer

The ratings here are the conservative chassis-wiring numbers for a single wire in free air, which is what hobby projects actually are. Keep the drop under about 3% for power wiring and under 10% for a lone LED strip you don't care much about. When in doubt, one gauge thicker costs cents and solves arguments.

The full AWG chart

AWG	Diameter	Resistance	Max current (chassis)	Typical duty
4	5.19 mm	0.815 Ω/km	60 A	battery and inverter cables
6	4.11 mm	1.3 Ω/km	55 A	battery and inverter cables
8	3.26 mm	2.06 Ω/km	40 A	battery and inverter cables
10	2.59 mm	3.28 Ω/km	30 A	mains and high-power DC
12	2.05 mm	5.21 Ω/km	25 A	mains and high-power DC
14	1.63 mm	8.29 Ω/km	20 A	speaker wire, 12 V accessories
16	1.29 mm	13.2 Ω/km	13 A	speaker wire, 12 V accessories
18	1.02 mm	21 Ω/km	10 A	hookup wire, LED strips
20	0.812 mm	33.3 Ω/km	6 A	hookup wire, LED strips
22	0.644 mm	53 Ω/km	5 A	breadboard jumpers, data
24	0.511 mm	84.2 Ω/km	3.5 A	breadboard jumpers, data
26	0.405 mm	134 Ω/km	2.2 A	wire-wrap, fine signals
28	0.321 mm	213 Ω/km	1.4 A	wire-wrap, fine signals
30	0.255 mm	339 Ω/km	0.86 A	wire-wrap, fine signals

Copper, single conductor in free air. Wires bundled in a sleeve carry much less; power-transmission tables cut these numbers roughly in half. Every three gauge steps doubles the copper area, and every ten steps multiplies resistance by ten.