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
BRANCH CONDUCTORConductor Length

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.

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
324242220181816
524222018161614
722201816141412
920181816141212
1020181616141212
1220181614121210
1518161414121010
181816141210108
201816141210108
22161414121088
24161412121088
3016141210886
4014121010866
501412108664
60121088644
70121086442
80121086442
9010886422
10010866422
1251086422N/A
15086442N/AN/A
Feeder Conductor (multiple loads)
Conductor Voltage Drop
13.8V nominal voltage
5%
3%
2%
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