Irrigation & Lighting Division

Voltage Loss for Copper Wire (AWG)

The voltage losses in the chart below were calculated using Ohm's Law, and are theoretical. Safety margin should be built into the design to take into consideration deterioration of wire splices, power brownouts, etc.

FLOW
(AMPS)
VOLTAGE LOSS PER 1000' OF WIRE RUN (2 WIRES)
AMERICAN WIRE GAUGE (AWG)
18 16 14 14/12 14/10 12 10 8 6 4 2 1 0 00 000 0000
0.1 1.28 0.80 0.51 0.41 0.35 0.32 0.20 0.13 0.08 0.05 0.03 0.03 0.02 0.02 0.01 0.01
0.2 2.56 1.61 1.01 0.82 0.70 0.63 0.40 0.25 0.16 0.10 0.06 0.05 0.04 0.03 0.03 0.02
0.3 3.83 2.41 1.52 1.23 1.06 0.95 0.60 0.38 0.24 0.15 0.10 0.08 0.06 0.05 0.04 0.03
0.4 5.11 3.22 2.02 1.64 1.41 1.27 0.80 0.50 0.32 0.20 0.13 0.10 0.08 0.06 0.05 0.04
0.5 6.39 4.02 2.53 2.06 1.76 1.59 1.00 0.63 0.40 0.25 0.16 0.13 0.10 0.08 0.06 0.05
0.6 7.67 4.83 3.03 2.47 2.11 1.90 1.19 0.75 0.48 0.30 0.19 0.15 0.12 0.10 0.08 0.06
0.7 8.95 5.63 3.54 2.88 2.46 2.22 1.39 0.88 0.57 0.35 0.22 0.18 0.14 0.11 0.09 0.07
0.8 10.22 6.43 4.04 3.29 2.82 2.54 1.59 1.00 0.65 0.40 0.26 0.20 0.16 0.13 0.10 0.08
0.9 11.50 7.24 4.55 3.70 3.17 2.86 1.79 1.13 0.73 0.46 0.29 0.23 0.18 0.14 0.11 0.09
1.0 12.78 8.04 5.05 4.11 3.52 3.17 1.99 1.26 0.81 0.51 0.32 0.25 0.20 0.16 0.13 0.10
2.0 25.56 16.08 10.10 8.22 7.04 6.35 3.98 2.51 1.62 1.01 0.64 0.51 0.40 0.32 0.25 0.20
3.0 38.34 24.13 15.15 12.34 10.56 9.52 5.97 3.77 2.42 1.52 0.96 0.76 0.60 0.48 0.38 0.30
4.0 - 32.17 20.20 16.45 14.08 12.70 7.96 5.02 3.23 2.02 1.28 1.02 0.80 0.64 0.50 0.40
5.0 - 40.21 25.25 20.56 17.60 15.87 9.95 6.28 4.04 2.53 1.60 1.27 1.00 0.80 0.63 0.50
6.0 - 48.25 30.30 24.67 21.12 19.04 11.94 7.54 4.85 3.04 1.92 1.52 1.20 0.96 0.76 0.60
7.0 - - 35.35 28.78 24.64 22.22 13.93 8.79 5.66 3.54 2.24 1.78 1.40 1.12 0.88 0.70
8.0 - - 40.40 32.90 28.16 25.39 15.92 10.05 6.46 4.05 2.56 2.03 1.60 1.28 1.01 0.80
9.0 - - 45.45 37.01 31.68 28.57 17.91 11.30 7.27 4.55 2.88 2.29 1.80 1.44 1.13 0.90
10.0 - - 50.50 41.12 35.20 31.74 19.90 12.56 8.08 5.06 3.20 2.54 2.00 1.60 1.26 1.00
COPPER WIRE RESISTANCE (OHMS PER 1000' OF SINGLE WIRE) @ 68ºF
WIRE GAUGE (AWG)
18 16 14 14/12 14/10 12 10 8 6 4 2 1 0 00 000 0000
6.390 4.021 2.525 2.056 1.760 1.587 0.995 0.628 0.404 0.253 0.160 0.127 0.100 0.080 0.063 0.050
note:
  1. These figures were derived by using Ohm's law and the above values for copper wire resistance, which were obtained from Table 8 of the 2005 edition of the National Electrical Code.
  2. The distances should be reduced by 20% as a safety factor for losses caused by corrosion to connections, equipment deterioration, brownouts, etc.
  3. The heading 14/12 means 14 AWG "hot" wire and 12 AWG "common" wire
  4. Based on operating temperature of 68°F (20°C)