Voltage Drop Calculator by electrician.com

The following calculator calculates the voltage drop, and voltage at the end of the wire for American Wire Gauge from 4/0 AWG to 30 AWG, aluminum or copper wire.

Select Copper or Aluminum:
Select American Wire Gauge (AWG) Size:
Select Voltage:
Enter 1-way circuit length in feet:
Enter Load in amps:

Voltage drop:
Voltage at load end of circuit:
Per Cent voltage drop:
Wire cross section in circular mils:


Load Carrying Capacities (see table below)
The following chart is a guideline of ampacity or copper wire current carrying capacity following the Handbook of Electronic Tables and Formulas for American Wire Gauge. As you might guess, the rated ampacities are just a rule of thumb. The Maximum Amps for Power Transmission uses the 700 circular mils per amp rule, which is very very conservative. The Maximum Amps for Chassis Wiring is also a conservative rating, but is meant for wiring in air, and not in a bundle. For short lengths of wire, such as is used in battery packs you should trade off the resistance and load with size, weight, and flexibility.
AWG gauge Diameter Inches Diameter mm Ohms per 1000 ft Ohms per km Maximum amps for chassis wiring Maximum amps for power transmission
OOOO 0.46 11.684 0.049 0.16072 380 302
OOO 0.4096 10.40384 0.0618 0.202704 328 239
OO 0.3648 9.26592 0.0779 0.255512 283 190
0 0.3249 8.25246 0.0983 0.322424 245 150
1 0.2893 7.34822 0.1239 0.406392 211 119
2 0.2576 6.54304 0.1563 0.512664 181 94
3 0.2294 5.82676 0.197 0.64616 158 75
4 0.2043 5.18922 0.2485 0.81508 135 60
5 0.1819 4.62026 0.3133 1.027624 118 47
6 0.162 4.1148 0.3951 1.295928 101 37
7 0.1443 3.66522 0.4982 1.634096 89 30
8 0.1285 3.2639 0.6282 2.060496 73 24
9 0.1144 2.90576 0.7921 2.598088 64 19
10 0.1019 2.58826 0.9989 3.276392 55 15
11 0.0907 2.30378 1.26 4.1328 47 12
12 0.0808 2.05232 1.588 5.20864 41 9.3
13 0.072 1.8288 2.003 6.56984 35 7.4
14 0.0641 1.62814 2.525 8.282 32 5.9
15 0.0571 1.45034 3.184 10.44352 28 4.7
16 0.0508 1.29032 4.016 13.17248 22 3.7
17 0.0453 1.15062 5.064 16.60992 19 2.9
18 0.0403 1.02362 6.385 20.9428 16 2.3
19 0.0359 0.91186 8.051 26.40728 14 1.8
20 0.032 0.8128 10.15 33.292 11 1.5
21 0.0285 0.7239 12.8 41.984 9 1.2
22 0.0254 0.64516 16.14 52.9392 7 0.92
23 0.0226 0.57404 20.36 66.7808 4.7 0.729
24 0.0201 0.51054 25.67 84.1976 3.5 0.577
25 0.0179 0.45466 32.37 106.1736 2.7 0.457
26 0.0159 0.40386 40.81 133.8568 2.2 0.361
27 0.0142 0.36068 51.47 168.8216 1.7 0.288
28 0.0126 0.32004 64.9 212.872 1.4 0.226
29 0.0113 0.28702 81.83 268.4024 1.2 0.182
30 0.01 0.254 103.2 338.496 0.86 0.142
31 0.0089 0.22606 130.1 426.728 0.7 0.113
32 0.008 0.2032 164.1 538.248 0.53 0.091
Metric 2.0 0.00787 0.200 169.39 555.61 0.51 0.088
33 0.0071 0.18034 206.9 678.632 0.43 0.072
Metric 1.8 0.00709 0.180 207.5 680.55 0.43 0.072
34 0.0063 0.16002 260.9 855.752 0.33 0.056
Metric 1.6 0.0063 0.16002 260.9 855.752 0.33 0.056
35 0.0056 0.14224 329 1079.12 0.27 0.044
Metric 1.4 .00551 .140 339 1114 0.26 0.043
36 0.005 0.127 414.8 1360 0.21 0.035
Metric 1.25 .00492 0.125 428.2 1404 0.20 0.034
37 0.0045 0.1143 523.1 1715 0.17 0.0289
Metric 1.12 .00441 0.112 533.8 1750 0.163 0.0277
38 0.004 0.1016 659.6 2163 0.13 0.0228
Metric 1 .00394 0.1000 670.2 2198 0.126 0.0225
39 0.0035 0.0889 831.8 2728 0.11 0.0175
40 0.0031 0.07874 1049 3440 0.09 0.0137