12 volt Wire Gauge vs. Amps

12 Volt Wiring Gauge Requirements at specific Amps for Automotive Electrical Systems



To choose an adequate wire gauge, determine the amp draw (amperage) that the wire circuit will carry.  Then measure the distance that the wire will travel (length) including the length of the return to ground (the ground wire running to the chassis or back to a ground block or battery.  Using these two numbers, Amps and length, locate the nearest gauge value in chart below.  For 6 volt automotive systems typically a wire gauge 2 sizes larger than what is shown should be used.
 
Amps  
@ 12 Volts 		LENGTH OF WIRE
American Wire Gauge (AWG)
3' 5' 7' 10' 15' 20' 25'
0 to 1 18 18 18 18 18 18 18
1.5 18 18 18 18 18 18 18
2 18 18 18 18 18 18 18
3 18 18 18 18 18 18 18
4 18 18 18 18 18 18 18
5 18 18 18 18 18 18 18
6 18 18 18 18 18 18 16
7 18 18 18 18 18 18 16
8 18 18 18 18 18 16 16
10 18 18 18 18 16 16 14
11 18 18 18 18 16 16 14
12 18 18 18 18 16 16 14
15 18 18 18 18 14 14 12
18 18 18 16 16 14 14 12
20 18 18 16 16 14 12 10
22 18 18 16 14 12 12 10
24 18 18 16 14 12 12 10
30 18 16 14 12 10 10 10
36 16 14 14 12 10 10 10
40 16 14 12 12 10 10 8
50 16 14 12 10 10 10 8
100 12 12 10 10 6 6 4
150 10 10 8 8 4 4 2
200 10 8 8 6 4 4 2