Awg Copper Wire Table Current Limits
Awg Copper Wire Table Current Limits
Awg Copper Wire Table Current Limits
AWG Diam. (mils) Circular mils Ohms/1000ft Current Carrying Fusing Current Feet per Pound
0000
460
212000
0.050
1.56
000
410
168000
0.063
1.96
00
365
133000
0.077
2.4826
324.85
105531
0.096
3.1305
289.3
83694
0.1264
119.6
3.947
257.6
66358
0.1593
94.8
4.977
229.4
52624
0.2009
75.2
6.276
204.3
41738
0.2533
59.6
7.914
181.9
33088
0.3915
47.3
9.980
162
26244
0.4028
37.5
668
12.58
144.3
20822
0.5080
29.7
561
15.87
128.5
16512
0.6405
23.6
472
20.01
114.4
13087
0.8077
18.7
396
25.23
10
101.9
10384
1.018
14.8
333
31.82
11
90.7
8226
1.284
11.8
280
40.12
12
80.8
6529
1.619
9.33
235
50.59
13
72.0
5184
2.042
7.40
197
63.80
14
64.1
4109
2.575
5.87
166
80.44
15
57.1
3260
3.247
4.65
140
101.4
16
50.8
2581
4.094
3.69
117
127.9
17
45.3
2052
5.163
2.93
98.4
161.3
18
40.3
1624
6.510
2.32
82.9
203.4
19
35.9
1289
8.210
1.84
69.7
256.5
20
32.0
1024
10.35
1.46
58.4
323.4
21
28.5
812
13.05
1.16
407.8
22
25.3
640
16.46
.918
41.2
514.12
23
22.6
511
20.76
.728
648.4
24
20.1
404
26.17
.577
29.2
817.7
25
17.9
320
33.0
.458
1031
26
15.9
253
41.62
.363
20.5
1300
27
14.2
202
52.48
.288
1639
28
12.6
159
66.17
.228
14.4
2067
29
11.3
128
83.44
.181
2607
30
10.0
100
105.2
.144
10.2
3287
31
8.9
79
132.7
.114
4145
32
8.0
64
167.3
.090
5227
33
7.1
50.125
211.0
.072
6591
34
6.3
39.75
266.0
.057
5.12
8310
35
5.6
31.5
335
.045
4.28
10480
36
5.0
25.0
423
.036
3.62
13210
37
4.45
19.83
533
.028
16660
38
3.97
15.7
673
.022
2.5
21010
39
3.5
12.47
848
.018
26500
40
3.14
9.89
1070
.014
1.77
33410
41
2.8
7.842
1.52
42
2.494
6.219
1.28
43
2.221
4.932
1.060
44
1.978
3.911
0.916
45
1.761
3.102
46
1.568
2.460
47
1.397
1.951
48
1.244
1.547
49
1.107
1.227
50
0.986
0.973
wiring, as this page relates to electronic equipment wiring. For reference, the ampacity of copper wire at 30 0C for common wire sizes
14 AWG may carry a maximum of 20 Amps in free air, or 15 Amps as part of a 3 conductor cable.
12 AWG may carry a maximum of 25 Amps in free air, or 20 Amps as part of a 3 conductor cable.
10 AWG may carry a maximum of 40 Amps in free air, or 30 Amps as part of a 3 conductor cable.
8 AWG may carry a maximum of 70 Amps in free air, or 50 Amps as part of a 3 conductor cable.
The wire fusing [melting] current is based on the material the wire is made of, the diameter of the wire and the melting point of the the
material. The wire fusing current of a wire is provided in tables as constant current or as [a larger] current for some given amount of
time.
This formula is used on a few different sites [un-verified]; I=Ad(3/2) @ d is in inches, A is a constant: A = 10,244 for Copper. A = 7,585
for Aluminum.
I have listed a number of values for fusing current in the table above, for selected AWG sizes.
Aluminum wire properties are listed under on the Aluminum electrical Wire page
Manufacturers listing for electrical Wire and Cable {This Web Site}
Cable manufacturers will provide different numbers based on the insulation used for the wire.
Use the table below to off-set the conservative current carrying numbers in the table above, and the fusing current. The table below
lists copper wire with a Teflon [TFE] insulation. Teflon insulation has a higher operation temperature range then other insulators, for
example PVC. The table below is based on data derived from MIL-STD-975, using 700C as the operating temperature. To derate based
on number of wires in a bundle:
IBW = ISW x (29 - #wire) / 28 @ [1 to 15 Bundled wires]
IBW = ISW x (0.5) @ [more then 15 Bundled wires]
ISW = Single wire
IBW = Bundled wires
To derate by temperature use; derate by 80% at 1500C, 70% at 1350C, or 50% at 1050C (per MIL-STD-975)
Current Carrying
AWG
Current Carrying
00
169
147
108
81
60
44
10
33
12
25
14
19
16
13
18
9.2
20
6.5
22
4.5
24
3.3
26
2.5
28
1.8
30
1.3
DC Wire Table
This is a five percent table which means at these amperage ratings at the listed distances, 5% of
the power would be lost to resistance. Five percent is normally acceptable in low voltage systems,
but if you want a 2% figure, divide the given distances by 2.5. For a 10% loss multiply the
distance by 2. For distances at 48 volts, double the 24 volt distances for a 5 percent loss figure. For
240 volt 5% loss, double the 120 volt distances. These distances include the NEC requirement for
current over sizing of 25%.
Example: For a pump drawing 9 amperes at 24 volts, located 88 feet from the battery bank: look at
the center table for 24 volts. In the far left column find the next number higher than 9 (which is 10)
and follow that line across the table until you find a distance figure greater than 88. At the top of
the column find the gauge of wire (#8) that should be used. This method insures that wire losses
are kept to an acceptable level without spending too much money on extra-heavy cable. Using a
heavier wire than indicated, however, will result in even higher efficiencies and we do sometimes
invest in the next larger gauge. Wire can get expensive, and it may not be worth the money to get
that last 1% if you have to go to a much larger wire size.
Some of the newer grid tie systems inverters, such as the Sunny Boy, use up to 600 volts DC. Generally in these
systems loss in wire is nothing to worry about. HOWEVER - you will have to be more careful about selecting and
installing the wiring - high voltage DC is not something you want to do a 2nd rate wiring job on. Make sure the
insulation is rated for 600 volts, and that there is no damage to the wire or insulation.
We have also included a wire chart for converting Metric to AWG (American Wire gauge)
sizes.
All distances are in FEET
Do not use any wire sizes that might fall into the red zone - this would exceed the amperage rating of the wire
and it may overheat and burn.
#14
#12
#10
#8
240
422
656
480
187
328
516
720
141
225
328
562
960
103
159
272
422
#6
666
#4
#2
1/0
2/0
3/0
10
1200
84
131
216
337
534
15
1800
56
84
131
225
356
562
20
2400
65
103
1-8
272
422
675
25
3000
84
131
216
337
543
30
3600
65.63
112
178
281
450
722
40
4800
84
131
216
337
543
675
50
6000
67
103
171
272
431
543
684
24 Volt DC chart
Amps
in Wire
Watts
at 24V
#14
#12
#10
#8
#6
#4
#2
1/0
2/0
3/0
24
169
262
412
675
48
84
131
207
337
532
96
37
66
103
169
267
144
28
45
66
112
178
282
192
21
32
54
84
133
216
10
240
17
26
43
67
107
169
270
15
360
11
17
26
45
71
112
180
289
20
480
13
21
37
54
84
135
217
270
343
25
600
17
26
43
67
108
172
217
274
30
720
13
22
36
56
90
144
180
228
40
960
17
26
43
67
108
135
171
50
1200
13
21
34
54
86
108
137
12 Volt DC chart
Amps in Watts at
Wire
12V
#14
#12
#10
#8
#6
#4
#2
1/0
2/0
3/0
12
84
131
206
337
532
24
42
66
103
168
266
432
675
48
18
33
52
84
133
216
337
543
675
72
14
22
33
56
89
141
225
360
450
570
96
10
16
27
42
66
108
168
272
338
427
10
120
8.5
13
22
33
53
84
135
218
270
342
15
180
8.5
13
22
35
56
90
144
180
228
20
240
6.6
10
16
27
42
67
108
135
171
25
300
13
22
33
54
86
108
137
30
360
40
480
6.6
11
18
28
45
72
90
114
13
21
33
54
67
85
These are one-way distances, measured from point A to point B. The out and
back nature of electrical circuits has already been included. For PV arrays,
figure the entire run, from the panels to the charge controller to the batteries
mm2
AWG
mm2
AWG
mm2
AWG
mm2
30
0.05
18
0.75
16
4/0
120
28
0.08
17
1.0
25
300MCM
150
26
0.14
16
1.5
35
350MCM
185
24
0.25
14
2.5
50
500MCM
240
22
0.34
12
4.0
1/0
55
600MCM
300
21
0.38
10
6.0
2/0
70
750MCM
400
20
0.50
10
3/0
95
1000MCM
500
Metric Size
AWG Size
mm2
0.5
20
0.8
18
1.0
16
2.0
14
3.0
12
5.0
10
8.0
13.0
19.0
32.0
52.0
20
0.03196118
18
0.040303
16
0.0508214
14
0.064084
12
0.08080810
10
0.10189
0.128496
0.16202
0.18194
0.20431
0.22942
0.25763
0.2893
0.32486
00
0.3648
Circuit
Amperes
Circuit Watts
6V
12V
6V
12V
3'
5'
7'
10'
15'
20'
25'
0 to
2.5
0 to 5
15
30
18
18
18
18
18
18
18
3.0
18
36
18
18
18
18
18
18
16
3.5
21
42
18
18
18
18
18
18
16
4.0
24
48
18
18
18
18
18
16
16
5.0
10
30
60
18
18
18
18
16
16
16
5.5
11
33
66
18
18
18
18
16
16
14
6.0
12
36
72
18
18
18
18
16
16
14
7.5
15
45
90
18
18
18
18
14
14
12
9.0
18
54
108
18
18
16
16
14
14
12
10
20
60
120
18
18
16
16
14
12
10
11
22
66
132
18
18
16
16
12
12
10
12
24
72
144
18
18
16
16
12
12
10
15
30
90
180
18
16
16
14
10
10
10
20
40
120
240
18
16
14
12
10
10
25
50
150
300
16
14
12
12
10
10
50
100
300
600
12
12
10
10
75
150
450
900
10
10
100
200
600
1200
10
Find the amperes or watts the circuit is expected to carry on the left and the distance the
wiring must run at the top - follow the columns until they intersect - for example, a 12
volt circuit which is 15 feet long and carries 10 amperes should use at least 16 gauge
wire.
solid
conductor
copper
OOOO 0.46
11.684
0.049
0.16072 380
302
125 Hz
OOO
0.4096
239
160 Hz
OO
0.3648
9.26592
190
200 Hz
0.3249
8.25246
150
250 Hz
0.2893
7.34822
119
325 Hz
0.2576
6.54304
94
410 Hz
0.2294
5.82676
0.197
0.64616 158
75
500 Hz
0.2043
5.18922
60
650 Hz
0.1819
4.62026
47
810 Hz
0.162
4.1148
37
1100 Hz
0.1443
3.66522
0.4982 1.634096 89
30
1300 Hz
0.1285
3.2639
0.6282 2.060496 73
24
1650 Hz
0.1144
2.90576
0.7921 2.598088 64
19
2050 Hz
10
0.1019
2.58826
0.9989 3.276392 55
15
2600 Hz
11
0.0907
2.30378
1.26
4.1328
47
12
3200 Hz
12
0.0808
2.05232
1.588
5.20864 41
9.3
4150 Hz
13
0.072
1.8288
2.003
6.56984 35
7.4
5300 Hz
14
0.0641
1.62814
2.525
8.282
32
5.9
6700 Hz
15
0.0571
1.45034
3.184
10.44352 28
4.7
8250 Hz
16
0.0508
1.29032
4.016
13.17248 22
3.7
11 k Hz
17
0.0453
1.15062
5.064
16.60992 19
2.9
13 k Hz
18
0.0403
1.02362
6.385
20.9428 16
2.3
17 kHz
19
0.0359
0.91186
8.051
26.40728 14
1.8
21 kHz
20
0.032
0.8128
10.15
33.292
11
1.5
27 kHz
21
0.0285
0.7239
12.8
41.984
1.2
33 kHz
22
0.0254
0.64516
16.14
52.9392 7
0.92
42 kHz
23
0.0226
0.57404
20.36
66.7808 4.7
0.729
53 kHz
24
0.0201
0.51054
25.67
84.1976 3.5
0.577
68 kHz
25
0.0179
0.45466
32.37
106.1736 2.7
0.457
85 kHz
26
0.0159
0.40386
40.81
133.8568 2.2
0.361
107 kH
27
0.0142
0.36068
51.47
168.8216 1.7
0.288
130 kHz
28
0.0126
0.32004
64.9
212.872 1.4
0.226
170 kHz
29
0.0113
0.28702
81.83
268.4024 1.2
0.182
210 kHz
30
0.01
0.254
103.2
338.496 0.86
0.142
270 kHz
31
0.0089
0.22606
130.1
426.728 0.7
0.113
340 kHz
32
0.008
0.2032
164.1
538.248 0.53
0.091
430 kHz
Metric
0.00787
2.0
0.200
169.39 555.61
33
0.18034
Metric
0.00709
1.8
34
0.51
0.088
440 kHz
206.9
678.632 0.43
0.072
540 kHz
0.180
207.5
680.55
0.43
0.072
540 kHz
0.0063
0.16002
260.9
855.752 0.33
0.056
690 kHz
Metric
0.0063
1.6
0.16002
260.9
855.752 0.33
0.056
690 kHz
35
0.14224
329
1079.12 0.27
0.044
870 kHz
Metric
.00551
1.4
.140
339
1114
0.26
0.043
900 kHz
36
0.127
414.8
1360
0.21
0.035
1100 kHz
Metric
.00492
1.25
0.125
428.2
1404
0.20
0.034
1150 kHz
37
0.1143
523.1
1715
0.17
0.0289
1350 kHz
Metric
.00441
1.12
0.112
533.8
1750
0.163
0.0277
1400 kHz
38
0.1016
659.6
2163
0.13
0.0228
1750 kHz
Metric
.00394
1
0.1000
670.2
2198
0.126
0.0225
1750 kHz
39
0.0035
0.0889
831.8
2728
0.11
0.0175
2250 kHz
40
0.0031
0.07874
1049
3440
0.09
0.0137
2900 kHz
0.0071
0.0056
0.005
0.0045
0.004
18 AWG
Select Voltage
Enter Load
in amps
Voltage drop
This chart of American Wire Gauge (AWG) wire sizes and rated ampacities is data intended for the
pleasure of our readers only. Typographical errors, etc. are probable, since the typist is not a
professional (our CEO). Please point out errors. The data listed are incomplete and should be used
as a guideline only. Please contact manufacturers for the latest data.
Conductor size
It should be common-sense knowledge that liquids flow through large-diameter pipes easier than they do through small-diameter pipes (if you would
like a practical illustration, try drinking a liquid through straws of different diameters). The same general principle holds for the flow of electrons through
conductors: the broader the cross-sectional area (thickness) of the conductor, the more room for electrons to flow, and consequently, the easier it is for
flow to occur (less resistance).
Electrical wire is usually round in cross-section (although there are some unique exceptions to this rule), and comes in two basic varieties: solid and
stranded. Solid copper wire is just as it sounds: a single, solid strand of copper the whole length of the wire. Stranded wire is composed of smaller
strands of solid copper wire twisted together to form a single, larger conductor. The greatest benefit of stranded wire is its mechanical flexibility, being
able to withstand repeated bending and twisting much better than solid copper (which tends to fatigue and break after time).
Wire size can be measured in several ways. We could speak of a wire's diameter, but since its really the cross-sectional area that matters most
regarding the flow of electrons, we are better off designating wire size in terms of area.
The wire cross-section picture shown above is, of course, not drawn to scale. The diameter is shown as being 0.1019 inches. Calculating the area of the
cross-section with the formula Area = r2, we get an area of 0.008155 square inches:
These are fairly small numbers to work with, so wire sizes are often expressed in measures of thousandths-of-an-inch, or mils. For the illustrated
example, we would say that the diameter of the wire was 101.9 mils (0.1019 inch times 1000). We could also, if we wanted, express the area of
the wire in the unit of square mils, calculating that value with the same circle-area formula, Area = r 2:
However, electricians and others frequently concerned with wire size use another unit of area measurement tailored specifically for wire's circular crosssection. This special unit is called the circular mil (sometimes abbreviated cmil). The sole purpose for having this special unit of measurement is to
eliminate the need to invoke the factor (3.1415927 . . .) in the formula for calculating area, plus the need to figure wireradius when you've been
given diameter. The formula for calculating the circular-mil area of a circular wire is very simple:
Because this is a unit of area measurement, the mathematical power of 2 is still in effect (doubling the width of a circle will always quadruple its area,
no matter what units are used, or if the width of that circle is expressed in terms of radius or diameter). To illustrate the difference between
measurements in square mils and measurements in circular mils, I will compare a circle with a square, showing the area of each shape in both unit
measures:
Obviously, the circle of a given diameter has less cross-sectional area than a square of width and height equal to the circle's diameter: both units of
area measurement reflect that. However, it should be clear that the unit of "square mil" is really tailored for the convenient determination of a square's
area, while "circular mil" is tailored for the convenient determination of a circle's area: the respective formula for each is simpler to work with. It must
be understood that both units are valid for measuring the area of a shape, no matter what shape that may be. The conversion between circular mils and
square mils is a simple ratio: there are (3.1415927 . . .) square mils to every 4 circular mils.
Another measure of cross-sectional wire area is the gauge. The gauge scale is based on whole numbers rather than fractional or decimal inches. The
larger the gauge number, the skinnier the wire; the smaller the gauge number, the fatter the wire. For those acquainted with shotguns, this inverselyproportional measurement scale should sound familiar.
The table at the end of this section equates gauge with inch diameter, circular mils, and square inches for solid wire. The larger sizes of wirereach an
end of the common gauge scale (which naturally tops out at a value of 1), and are represented by a series of zeros. "3/0" is another way to represent
"000," and is pronounced "triple-ought." Again, those acquainted with shotguns should recognize the terminology, strange as it may sound. To make
matters even more confusing, there is more than one gauge "standard" in use around the world. For electrical conductorsizing,
the American Wire Gauge (AWG), also known as the Brown and Sharpe (B&S) gauge, is the measurement system of choice. In Canada and Great
Britain, the British Standard Wire Gauge (SWG) is the legal measurement system for electrical conductors. Other wire gauge systems exist in the world
for classifying wire diameter, such as the Stubs steel wire gauge and the Steel Music Wire Gauge (MWG), but these measurement systems apply to nonelectrical wire use.
The American Wire Gauge (AWG) measurement system, despite its oddities, was designed with a purpose: for every three steps in the gauge
scale, wire area (and weight per unit length) approximately doubles. This is a handy rule to remember when making rough wire size estimations!
For very large wire sizes (fatter than 4/0), the wire gauge system is typically abandoned for cross-sectional area measurement in thousands of circular
mils (MCM), borrowing the old Roman numeral "M" to denote a multiple of "thousand" in front of "CM" for "circular mils." The following tableof wire sizes
does not show any sizes bigger than 4/0 gauge, because solid copper wire becomes impractical to handle at those sizes. Strandedwire construction is
favored, instead.
39
40
41
42
43
44
-------------------------------------
0.003531
0.003145
0.002800
0.002494
0.002221
0.001978
-------------------------------------
12.47
9.888
7.842
6.219
4.932
3.911
-------------------
0.000009793
0.000007766
0.000006159
0.000004884
0.000003873
0.000003072
0.03774
0.02993
0.02374
0.01882
0.01493
0.01184
For some high-current applications, conductor sizes beyond the practical size limit of round wire are required. In these instances, thick bars of solid
metal called busbars are used as conductors. Busbars are usually made of copper or aluminum, and are most often uninsulated. They are physically
supported away from whatever framework or structure is holding them by insulator standoff mounts. Although a square or rectangular cross-section is
very common for busbar shape, other shapes are used as well. Cross-sectional area for busbars is typically rated in terms of circular mils (even for
square and rectangular bars!), most likely for the convenience of being able to directly equate busbar size with round wire.
REVIEW:
Electrons flow through large-diameter wires easier than small-diameter wires, due to the greater cross-sectional area they have in which to
move.
Rather than measure small wire sizes in inches, the unit of "mil" (1/1000 of an inch) is often employed.
The cross-sectional area of a wire can be expressed in terms of square units (square inches or square mils), circular mils, or "gauge" scale.
Calculating square-unit wire area for a circular wire involves the circle area formula:
Calculating circular-mil wire area for a circular wire is much simpler, due to the fact that the unit of "circular mil" was sized just for this
purpose: to eliminate the "pi" and the d/2 (radius) factors in the formula.
Wire Size
Recently, there has been numerous questions on this board concerning the proper type or size of AC power
cable to use with different amounts of equipment. It is very important to use the correct size cable to insure
all the power will be available to your equipment and there is no danger of a fire or short from your cables.
Here is a Cable/Current table to help you select the proper one to use in your application.
Wire Size (AWG) 2 Conductor 3 Conductor 4 Conductor
10
30Amp
25
20
12
25
20
16
14
18
15
12
16
13
10
8
18
10
7
6
Notice that the smaller the AWG number, the more current it can handle. All Extension Cords are required to
list the wire gauge. That will tell you the amount of current they can safely handle.
The wire in the above example is Copper type and of the same temperature rating. All currents listed are for
Ambient temperature. Keep in mind that there are also many different type of insulation material that will
determine the temperature rating. The wire may not be pure copper but an alloyed of aluminum, nickel, tin
and copper.
Standard cable, as used in home and general construction, is classified by the wire size, number of wires,
insulation type and dampness condition of the wire environment.
Example: a cable with the code "12/2 with Ground Type UF 600V (UL)" has the following
specifications:
1. Wire size is 12 gauge (minimum required size for homes today).
2. The "/2" indicates there are two wires in the cable.
3. "Ground" indicates there is a third wire in the cable to be used as a grounding
wire.
4. "Type UF" indicates the insulation type and acceptable dampness rating.
5. "600V" means the wire is rated at 600 volts maximum.
6. "UL" indicates the wire has been certified by Underwriters Laboratory to be
safe.
Standard wire color codes are very different between electronic circuitry and
household 110 Volt AC wiring.
Household wiring (or other AC applications in the 100+ volt range) use the following color codes:
BLACK "Hot" wire. Connected to Brass colored terminal.
GREEEN "Ground" wire. Also called chassis ground.
RED "Traveler" wire. Used for 3-ways switches.
WHITE "Neutral" wire. Connected to silver colored terminal.
VOLTAGE DROP vs. WIRE SIZE
Voltage drop is the amount of voltage lost over the length of a circuit. Voltage drop changes as a function of
the resistance of the wire and should be less than 2% if possible. If the drop is greater than 2%, efficiency of
the equipment in the circuit is severely decreased and life of the equipment will be decreased. As an
example, if the voltage drop on an incandescent light bulb is 10%, the light output of the bulb decreases over
30%!
Voltage drop can be calculated using Ohmss Law, which is:
Voltage Drop = Current in amperes x Resistance in ohms.
For example, the voltage drop over a 200 foot long, #14 copper wire, power line supplying a 1000 watt
floodlight is calculated as follows:
Current = 1000watts/120volts = 8.33 amperes
Resistance of #14 copper wire = 2.58ohms/1000feet
Resistance of powerline=2 x 200ft x 0.00258ohms/ft=1.032ohms
Voltage drop = 8.33 amperes x 1.032 ohms = 8.60 volts
Percent voltage drop = 8.60volts/120volts = 7.2%
The 7.2% drop is over the maximum 2% so either the wattage of the bulb must be decreased or the diameter
of the wire must be increased (a decrease in wire gauge number). If #9 copper wire were used in the above
example, the voltage drop would have only been 2.2%.
A more commonly used method of calculating voltage drop is as follows:
Voltage Drop =
Short Table
AWG
mm2
AWG
mm2
AWG
mm2
AWG
mm2
30
0.05
18
0.75
16
4/0
120
28
0.08
17
1.0
25
300MCM
150
26
0.14
16
1.5
35
350MCM
185
24
0.25
14
2.5
50
500MCM
240
22
0.34
12
4.0
1/0
55
600MCM
300
21
0.38
10
6.0
2/0
70
750MCM
400
20
0.50
10
3/0
95
1000MCM
500
AWG
Diameter
Diameter
mm
inch
Square
mm2
Resistance
Resistance
ohm/km
ohm/1000 feet
46
0,04
0,0013
13700
44
0,05
0,0020
8750
42
0,06
0,0028
6070
41
0,07
0,0039
4460
40
0,08
0,0050
3420
39
0,09
0,0064
2700
Amps
Watts
#16
1080
#14
12
1440
#12
16
1920
#10
24
2880
#8
32
3840
#6
40
4800
#4
48
5760
Gauge
Amps
Watts
#16
2160
#14
12
2880
#12
16
3840
#10
24
5760
#8
32
7680
#6
40
9600
#4
48
11520
Run Length
Amps
100
150
150' - 200'
200- 250'
250'
250' - 300'
300
400'
400-500
500'
300' - 400'
12
#12
#10
#8
#6
16
#10
#8
#6
24
#8
#6
#4
32
#6
#4
#2
40
#6
#4
#4
#4
#2
#2
#2
#1
#1
#1/0
#1/0
#2/0
Note:
For every extra 50 feet of cable/wire up to #8 normally you upgrade to the next size, consult you local codes if your unsure about double and triple length runs.
Ex: #6 is sometimes mandatory for a 200 foot 12 amp run but can be used up to 300 feet on a 12 amp circuit.
Note:
Each time an additional plug is used in line of the run using 80% safe load, subtract an additional 2% from the over all power usage (80% to 78%).
Ex: One plug into the wall counts as your one 'free' plug.
WARNING: extension cords ARE included into the total length from breaker box (+25 feet and one gauge up), if intended for continuous use at said MAX safe
power usage.
In addition, you need to make sure you getting what is actually equal to said gauge (if your making you own cord from something like SJO cable).
Recently, I have found that some places go by size and not current. A 12 gauge standard wire is actually the size of 10 gauge solid. This is to make up for it not
being a solid connector. Bring something with you to compare wire size with what's printed/stamped on the sheeting. It should be one gauge bigger in size than
what's on the sheeting.
Ex: If you have a 1000W light and are using a 12 amp circuit, you should use a 15amp #12 extension cord no longer than 25 feet.
This info isnt complete and probably doesnt apply to many, cuz if your thinking this big you should already have a general understanding of codes and loads.
#4 (approx 65-75A each) used for 100-115 amp service
#2 (approx 90A each) used for 125-150 amp service
#1/0 (approx 150A each) used for 200 amp service
#2/0 (approx 175A each) typically for industrial or vary long run with a large load. 300-350 amp service
#0/3 (approx 200A each) typically for industrial or vary long run with a large load. 400 amp service
Service cable is specifically designed for extra service lines and or extra long (In structure or over-head) runs. 1/0 Gauge I believe is the only service cable (or
cable) sold connected as x/3 (retail), provides a path fore both hots, the neutral and ground.
Please specify wire / insulation /cable type. Tables fairly meaningless without.
There is no accurate rule of thumb for distance / wire upsizing. I'm afraid one must do the math here, particularly with the price of wire what it is.
"Recently, I have found that some places go by size and not current. A 12 gauge standard wire is actually the size of 10 gauge solid. This is to make up for it not
being a solid connector. Bring something with you to compare wire size with what's printed/stamped on the sheeting. It should be one gauge bigger in size than
what's on the sheeting."
Stranded wire is physically larger, but uses the same amount of copper. Carries the same amount of current. Solid wire dimension gauges are fairly worthless for
measuring stranded wire.
Stranded wire exhibits better electrical performance in AC circuits.
This page is to provide a single place to look to for what the safe rated capacities of various size
wires in general use. These are general guidelines - check with the wire manufacturer or standards
body controlling your installation for any additional specifications. Keep in mind that temperature
and environment have a dramatic effect on these ratings, and that for wiring it's much better to err
on the side of too large a wire than too small.
This page started as a page for 12V DC automotive use, but has grown over time to include a more
general set of information on wire sizing. I've tried to add some basic explanations of what matters
when sizing a wire and to avoid using too many details specific to certain applications. The actual
formulas used to figure this out can be very complex - for example the National Electrical Code
specifies the wire sizes to be used in excruciating detail based on years of actual research on what
happens to wires in The Real World. Keeping up with all those details can be very hard, but the
basic principles are pretty straightforward. My goal for this page is to expose you to those basic
concepts, and at the end to give a basic "rule of thumb" chart for folks to start out with.
This page was created to help explain concepts and give an overview of wire capacity and what is
factored into deciding on the wire size to use in a given application. This page should not to be
considered an authoritative source of exact numbers on what wire size to use. Consult other
sources such as wiring codes and manufacturers recommendations on the piece of equipment you
are installing for more details. I am not telling you what wire size to use - the information here is
provided as-is and without any guarantee as to it's accuracy or completeness. Any issues caused by
the use of this information are not my fault - be smart, use common sense, and use this
information at your own risk.
surrounding material in some cases. Electrical fires are nasty and tend to start in the hardest to
reach places - where the most heat builds up back in dark corners and tight spaces. This is why
using the right size wires is important for your safety and for safety of others using your wiring
work.
In some respects, the capacity of a wire is actually best measured in watts, not amperage. Why?
Because a watt is a unit or power that is a combination of amperage (volume), voltage (pressure),
and resistance to the power flowing through that wire. Watts measure the amount of power (aka,
heat) a wire can safely dissipate. However, most wire charts are done in amps. This is unfortunate
because it means the wire chart is sort of assumed to be at a single voltage level. For most usage,
this is fine because the chart has an assumed usage. As an example, charts for amperage ratings of
of various sizes wires for 110V AC house current charts are popular and reasonably well-known. On
the other hand, the amperage ratings are very different for common/typical 12V DC automotive
usage. For example, a 12 gauge wire is commonly rated at 20A for 110V AC home usage, but in
automotive 12V DC use 12 gauge wire is commonly used for circuits carrying 60A! A prime example
would be the main charging wire from the alternator to the battery and out to the main electrical
circuits of the car. I thought I had a satisfactory explanation posted here previously, but a few folks
took aim at it and blew gaping holes in my understanding - without actually explaining what I was
trying to understand or explain here. As of yet, I have not gotten a satisfactory explanation for this
discrepancy. No one I've talked to as of yet has been able to explain it to me, but if you think you
know the magic answer, please let me know. Maybe I'm missing something obvious. Maybe I'm just
not understanding this as well I as think I am. Who knows... At any rate, the chart below reflects
the difference in 110V AC vs. 12V DC usage, even though I'm still at a loss to explain the details.
Remember, if in doubt, it's always better to put in too big of a wire than too small of a wire.
requirement.
Wire Length
Since all wires have resistance, the longer the wire, the greater the resistance. This means that for
longer wiring runs you need to use a larger wire to compensate. This phenomenon is often referred
to as "voltage drop", and for lower voltage automotive systems, the loss of 2V or even 1V can be
significant. On longer wire runs, plan on using a larger size wire. There are specific voltage drop
calculations that depend on the wire size in use, the length of the wire, the load applied, and the
voltage in use. The National Electric Code has tons of charts for this, but there's a nifty online
voltage drop calculator that one of my readers pointed out to me that does 120V AC as well as 12V
DC - and even 6V DC. You'd be surprised at some of the voltage drops you can find just form the
wiring in use, so experiment with the calculator a bit to see if it's worth going to the next highest
size wire in your application. On automotive applications of only 12V, losing a single volt of power
in the wire is a whopping 8% loss, so it can be a big deal for voltage critical applications like your
headlights where more voltage = more light. Kudos to Ron White for providing me with the link to
that calculator, and kudos to the folks over at PowerStream.com for putting that calculator and
other data online.
Duration of Usage
Some electrical loads are continuous for long periods of times (like a light in your house or the
headlights on your car) and some are much more intermittent (like a garbage disposal in your house
or the starter in your car). This affects the wire size used - the longer a wire is in use, the more
heat it will tend to retain. A wire for something that is only used for short periods (like the starter
in your car) does not need quite as large of a wire as something that will be in use for very long
periods of time. This means that for long-duration uses, you must de-rate the wire even further
Electrical Calculations
There are four basic units of measurement for electricity:
There are a number of formulas that relate each of these four things - they all change in
relationship to one another such that if you know any two you can calculate the other two. Lots of
folks on the Internet have easy-to use calculators that allow you to do this online
- http://www.sengpielaudio.com/calculator-ohm.htm is one. The formula wheel below was on
their website and presents the info in a pretty easy to understand format.
Capacity Chart
This chart is a simple "max capacity" chart for a short wire run. Increase the wire size for long runs
- for example the wires running to the back of a vehicle to power the taillights may need to be one
size larger to account for the length.
Gauge
110V
12V
22
5A
5A
20
7.5A
8A
18
10A
10A
16
13A
20A
14
17A
40A
12
23A
60A
10
33A
100A
46A
150A
60A
??A
80A
??A
100A
??A
125A
??A
150A
??A
Chart Notes
This 110V column in this chart was provided by one of my readers and according to him it is based on
the data in The Howard W. Sams Engineering Staff fifth edition 1983 for stranded copper wire when
used in a conduit or bundle. (Open air ratings would be higher, solid copper wire ratings might be
slightly lower.) This data seems in line with commonly accepted usage for 120/220V home electrical
wiring.
The 12V column is based on various sources I have found across the Internet combined with the
accepted usage in various vehicles I have worked on. I am generally a bit skeptical of the max
capacity the sources I found claimed for some of the smaller wire sizes. For example, 16 gauge wire
is mighty thin to run 20A through for even a short distance, and this chart is
a conservative interpretation of the data I found out there. Some data had the max capacity even
higher than this - yikes!
The values here for 12V usage are not yet certified to be correct/valid/safe - they are my ballpark
figures based on what I believe to be true based on what I have learned. Consult other sources of
information for your specific application for more details.
One other consideration in electrical wiring is choosing the right wire type.
This usually refers to the insulation of the wire and its temperature rating.
Selecting the approapiate insulation type and temperature rating is important
and depnds on the environment and application of where the wire will be used.
Romex is an all purpose wire almost used exclusively in residential wiring
where the heat is not excessive and the wire is not subject to damage. Each
specific type of wire has its own application and temperature rating and must
be used in accordance with the NEC (National Electrical Code). Some wire is
rated for direct burial underground while other wire is not rated for direct
burial and must be used on conduit when run underground. Always refer to the
NEC or your local electrical inspector for rules pertaining to the type of wire
and the application.
The following chart shows the proper wire size or wire guage ( awg ) for the
desired current or amperage.
* The national electric code (NEC) specifies that the over-current protection
device (breaker, fuse, or motor over-load) not exceed 15A for 14 AWG wire,
20A for 12 AGW wire, and 30A for 10 AGW wire.
Aluminum
Wire Size
167 (75C) 194 (90C) 167 (75C) 194 (90C)
*14
20 (*15)
25
*12
25 (*20)
30
20
25
*10
35 (*30)
40
30
35
50
55
40
45
65
75
50
60
85
95
65
75
115
130
90
100
Copper
Wire Gauge
Size
Aluminum
60C
(140F)
75C
(167F)
90C
(194F)
75C
(167F)
90C
(194F)
NM-B
THW
THWN-2
THW
XHHW-2
UF-B
THWN
THHN
THWN
THHN
SE
XHHW-2
SE
THWN-2
USE
USE-2
USE
XHHW
XHHW
14
15
15
15
---
---
12
20
20
20
15
15
10
30
30
30
25
25
40
50
55
40
45
55
65
75
50
60
70
85
95
65
75
85
100
110
75
85
95
115
130
90
100
---
130
150
100
115
1/0
---
150
170
120
135
2/0
---
175
195
135
150
3/0
---
200
225
155
175
4/0
---
230
260
180
205
250
---
255
290
205
230
300
---
285
320
230
255
350
---
310
350
250
280
500
---
380
430
310
350
600
---
420
475
340
385
750
---
475
535
385
435
1000
---
545
615
445
500
AWG
DIAMETER
AREA
WEIGHT
(KILOGRAMS PER METER)
TURNS OF WIRE
(PER INCH)
0000 (4/0)
0.46" (11.7mm)
0.953
2.17
000 (3/0)
0.41" (10.4mm)
0.756
2.44
00 (2/0)
0.365" (9.27mm)
0.599
2.74
0.475
3.08
0.377
3.46
0.299
3.88
0.237
4.36
0.188
4.89
0.149
5.5
0.118
6.17
0.0938
6.93
0.0744
7.78
0.059
8.74
10
0.0468
9.81
11
0.0371
11
12
0.0294
12.4
13
0.0234
13.9
14
0.0185
15.6
15
0.0147
17.5
16
0.0116
19.7
17
0.00922
22.1
18
0.00732
24.8
19
0.0058
27.9
20
0.0046
31.3
21
0.00365
35.1
22
0.00289
39.5
23
0.00229
44.3
24
0.00182
49.7
25
0.00144
55.9
26
0.00114
62.7
27
0.000908
70.4
28
0.00072
79.1
29
0.000571
88.8
30
0.000453
99.7
31
0.000359
112
32
0.000285
126
33
0.000226
141
34
0.000179
159
35
0.000142
178
36
0.005" (0.127mm)
0.000113
200
37
0.0000893
225
38
0.0000708
252
39
0.0000562
283
40
0.0000445
318
Coaxial Cable (for cable TV and a few Ethernet applications): 18 and 20 AWG
Cat 5, Cat 5e, and Cat 6 cables (for LANs and Ethernet): 24 AWG
For more great information on American Wire Gauge, including wire diameter formula, check out Wikipedia's section on AWG.