Automotive Wire Size Calculator – Wire Gauge Chart

Automotive & Marine Wire Sizing Chart

20°C

40°C

50°C

60°C

70°C

80°C

90°C

100°C

Temperature correction factors for various ambient air temperatures per NEC standards

Table cell colors are for visual purposes only and do not indicate physical wire color or temperature.
While this wire gauge table outlines specifics for single copper conductors in Free Air per the NEC, your automotive electrical installation does not necessarily conform to a “Free Air” definition. Granted, your conductors are not installed in a heat encompassing shield such as metal conduit or PVC tube either. Your conductors may be held firmly inside (breathable) wire loom or sleeving, and may be tie-wrapped or secured with a multitude of other conductors.
However, we can appropriately suggest that you increase the Ambient Temperature correction factor to allow for any (or all of the above) heat restraints.
BRANCH CONDUCTOR	Conductor Length
	3’	5’	7’	10’	15’	20’	25’
Total Load Amps (A)	Gauge sizes are based on single copper conductor in free air per NEC standards
3	18	18	18	18	18	18	16
5	18	18	18	18	16	16	14
7	18	18	18	16	14	14	12
9	18	18	18	16	14	12	12
10	18	18	16	16	14	12	12
12	18	18	16	14	12	12	10
15	18	16	14	14	12	10	10
18	18	16	14	12	10	10	8
20	18	16	14	12	10	10	8
22	16	14	14	12	10	8	8
24	16	14	12	12	10	8	8
30	16	14	12	10	8	8	6
40	14	12	10	10	8	6	6
50	14	12	10	8	6	6	4
60	12	10	8	8	6	4	4
70	12	10	8	6	4	4	2
80	12	10	8	6	4	4	2
90	10	8	8	6	4	2	2
100	10	8	6	6	4	2	2
125	10	8	6	4	2	2	N/A
150	8	6	4	4	2	N/A	N/A

Feeder Conductor (multiple loads)

Conductor Voltage Drop

13.8V nominal voltage