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SOCKETS & PLUGS
HAR
10GAUGE WIRE
12GAUGE WIRE
14GAUGE WIRE
16GAUGE WIRE
18GAUGE WIRE
20GAUGE WIRE
*Recommended minimum wire gauge size for stop light and ground circuits.
Stop Light (Red)
Ground (White)
Single trailer (up to 50’ length)
12 Gauge
10 Gauge
Doubles trailer (2-28’ lengths)
12 Gauge
10 Gauge
Doubles trailer (2-40’ lengths)
10 Gauge
8 Gauge
Triples trailer (3-28’ lengths)
10 Gauge
8 Gauge
Total length of cable in circuit from battery to most distant lamp
12 Volt System
Amperes (Approx.)
Up To 30 Feet 40 Feet 50 Feet 60 Fee 80 Feet 100 Feet 120 Feet
Gauge Gauge Gauge Gauge Gauge Gauge Gauge
1.0
14
14
14
14 14
14
14
2
14
14
14
14 14
14
14
3
14
14
14
14 14
14
12
4
14
14
14
14 14
12
12
5
14
14
14
14 12
12
12
6
14
14
14
14 12
12
10
7
14
14
14
12 12
10
10
8
14
14
12
12 10
10
10
10
14
12
12
12 10
10
8
11
14
12
12
10 10
8
8
12
14
12
12
10 10
8
8
15
12
12
10
10 8
8
8
18
12
10
10
8 8
8
8
20
12
10
10
8 8
8
6
25
12
10
8
8 8
6
6
30
12
10
8
8 8
6
6
35
12
10
8
8 6
6
6
HOW TO SELECT SIZE OF ELECTRIC CABLE
Voltage drop is the primary consideration in selecting the proper electrical wire size. The length of wire in a circuit is the major
contributing factor to voltage drop. The table below may be used in determining adequate wire gauge sizes for specific lengths of
cable when the amperage requirements are known.
Example: A lamp is 38 ft. from the power source and requires 10 amperes. This figure, when rounded upwards to the nearest
column heading given in the table, is 40 ft. The wire gauge in the “40-ft. Column” corresponding to 10 amperes is No. 12.
Voltage Drop/Foot/Ampere
20 GAUGE
.0110
18 GAUGE
.0067
16 GAUGE
.0045
14 GAUGE
.0028
12 GAUGE
.0018
10 GAUGE WIRE
.0011
.180
.160
.140
.120
.100
.080
.060
.040
.020
0 5 10 15 20 25 30 35 40 45 50
Voltage Drop Per Foot
amperes
WIRE SIZE
SAE J560 Standards Conductor Identification
Wire Color Lamp and Signal Circuits
Wht
White Ground return to towing vehicle
Blk *Black Clearance, side marker & license plate lamps
Yel
Yellow Left hand turn signal & hazard signal lamps
Red
Red
Stop lamps and antilock devices
Grn
Green Right hand turn signal & hazard signal lamps
Brn *Brown Tail, clearance, side marker lamps &
identification lamps
Blu
Blue
Auxiliary/ABS power
*It is recommended to balance the circuits as practicable.
Cable size
gauge no.
(Copper)
Maximum current
carrying capacity
with 0.5 volt drop
length of
wire
in feet
Note: This table gives you the resistance of wire per foot so with ohms law V=I x R you can calculate
voltage drops on any of the above wire gauges at any current level and length. For example,
voltage drop in 50 ft. 10 AWG wire with 20 amp load is V=20 amp x (0.00103 Ω /ft.) x 50 ft. = 1.03
volts. Be sure to include both the positive and negative leads when calculating total wire length.
wire resistance ohms
(Ω)
per foot
20 Ga.
18 Ga.
16 Ga.
14 Ga.
12 Ga.
10 Ga.
8 Ga.
10 Ft.
10 Ft.
10 Ft.
10 Ft.
10 Ft.
10 Ft.
10 Ft.
4.74 Amps
7.53 Amps
11.98 Amps
19.05 Amps
30.30 Amps
48.16 Amps
76.59 Amps
0.01054
Ω
/ft.
0.00663
Ω
/ft.
0.00417
Ω
/ft.
0.00262
Ω
/ft.
0.00165
Ω
/ft.
0.00103
Ω
/ft.
0.00065
Ω
/ft.