# Voltage drop calculator

Wire / cable voltage drop calculator and how to calculate.

* @ 68°F or 20°C

** Results may change with real wires: different resistivity of material and number of strands in wire.

*** For wire length of 2x10ft, wire length should be 10ft.

### DC / single phase calculation

The voltage drop V in volts (V) is equal to the wire current I in amps (A) times 2 times one way wire length L in feet (ft) times the wire resistance per 1000 feet R in ohms (Ω/kft) divided by 1000:

*V*_{drop (V)} = *I*_{wire (A)} × *R*_{wire(Ω)}

= *I*_{wire (A)} × (2 × *L*_{(ft)} × *R*_{wire(Ω/kft)} / 1000_{(ft/kft)})

The voltage drop V in volts (V) is equal to the wire current I in amps (A) times 2 times one way wire length L in meters (m) times the wire resistance per 1000 meters R in ohms (Ω/km) divided by 1000:

*V*_{drop (V)} = *I*_{wire (A)} × *R*_{wire(Ω)}

= *I*_{wire (A)} × (2 × *L*_{(m)} × *R*_{wire (Ω/km)} / 1000_{(m/km)})

### 3 phase calculation

The line to line voltage drop V in volts (V) is equal to square root of 3 times the wire current I in amps (A) times one way wire length L in feet (ft) times the wire resistance per 1000 feet R in ohms (Ω/kft) divided by 1000:

*V*_{drop (V)} = √3 × *I*_{wire (A)} × *R*_{wire
(Ω)}

= 1.732 × *I*_{wire (A)}
× (*L*_{(ft)} × *R*_{wire
(Ω/kft)} / 1000_{(ft/kft)})

The line to line voltage drop V in volts (V) is equal to square root of 3 times the wire current I in amps (A) times one way wire length L in meters (m) times the wire resistance per 1000 meters R in ohms (Ω/km) divided by 1000:

*V*_{drop (V)} = √3 × *I*_{wire (A)} × *R*_{wire
(Ω)}

= 1.732 × *I*_{wire (A)}
× (*L*_{(m)} × *R*_{wire (Ω/km)} / 1000_{(m/km)})

### Wire diameter calculations

The n gauge wire diameter d_{n} in inches (in) is equal to 0.005in times 92 raised to the power of 36 minus gauge number n, divided by 39:

*d _{n}*

_{ (in)}= 0.005 in × 92

^{(36-n)/39}

The n gauge wire diameter d_{n} in millimeters (mm) is equal to 0.127mm times 92 raised to the power of 36 minus gauge number n, divided by 39:

*d _{n}*

_{ (mm)}= 0.127 mm × 92

^{(36-n)/39}

### Wire cross sectional area calculations

The n gauge wire's cross sercional area A_{n} in kilo-circular mils (kcmil) is equal to 1000 times the square wire diameter d in inches (in):

*A _{n}*

_{ (kcmil)}= 1000×

*d*

_{n}

^{2}= 0.025 in

^{2}× 92

^{(36-n)/19.5}

The n gauge wire's cross sercional area A_{n} in square inches (in^{2})
is equal to pi divided by 4 times the square wire diameter d in inches (in):

*A _{n}*

_{ (in}2

_{)}= (π/4)×

*d*

_{n}

^{2}= 0.000019635 in

^{2}× 92

^{(36-n)/19.5}

The n gauge wire's cross sercional area A_{n}
in square millimeters (mm^{2}) is equal to pi divided by 4 times the square wire diameter d in millimeters (mm):

*A _{n}*

_{ (mm}2

_{)}= (π/4)×

*d*

_{n}

^{2}= 0.012668 mm

^{2}× 92

^{(36-n)/19.5}

### Wire resistance calculations

The n gauge wire resistance R in ohms per kilofeet (Ω/kft) is equal to 0.3048×1000000000 times the wire's resistivity *ρ* in
ohm-meters (Ω·m) divided by 25.4^{2} times the cross sectional area *A _{n}* in square inches (in

^{2}):

*R*_{n (Ω/kft)} = 0.3048 × 10^{9} × *ρ*_{(Ω·m)} / (25.4^{2}
× *A _{n}*

_{ (in}2

_{)})

The n gauge wire resistance R in ohms per kilometer (Ω/km) is equal to 1000000000 times the wire's resistivity *ρ* in
ohm-meters (Ω·m) divided by the cross sectional area *A _{n}* in square millimeters (mm

^{2}):

*R*_{n (Ω/km)} = 10^{9}
× *ρ*_{(Ω·m)} / *A _{n}*

_{ (mm}2

_{)}

## AWG chart

AWG # | Diameter (inch) |
Diameter (mm) |
Area (kcmil) |
Area (mm ^{2}) |
---|---|---|---|---|

0000 (4/0) | 0.4600 | 11.6840 | 211.6000 | 107.2193 |

000 (3/0) | 0.4096 | 10.4049 | 167.8064 | 85.0288 |

00 (2/0) | 0.3648 | 9.2658 | 133.0765 | 67.4309 |

0 (1/0) | 0.3249 | 8.2515 | 105.5345 | 53.4751 |

1 | 0.2893 | 7.3481 | 83.6927 | 42.4077 |

2 | 0.2576 | 6.5437 | 66.3713 | 33.6308 |

3 | 0.2294 | 5.8273 | 52.6348 | 26.6705 |

4 | 0.2043 | 5.1894 | 41.7413 | 21.1506 |

5 | 0.1819 | 4.6213 | 33.1024 | 16.7732 |

6 | 0.1620 | 4.1154 | 26.2514 | 13.3018 |

7 | 0.1443 | 3.6649 | 20.8183 | 10.5488 |

8 | 0.1285 | 3.2636 | 16.5097 | 8.3656 |

9 | 0.1144 | 2.9064 | 13.0927 | 6.6342 |

10 | 0.1019 | 2.5882 | 10.3830 | 5.2612 |

11 | 0.0907 | 2.3048 | 8.2341 | 4.1723 |

12 | 0.0808 | 2.0525 | 6.5299 | 3.3088 |

13 | 0.0720 | 1.8278 | 5.1785 | 2.6240 |

14 | 0.0641 | 1.6277 | 4.1067 | 2.0809 |

15 | 0.0571 | 1.4495 | 3.2568 | 1.6502 |

16 | 0.0508 | 1.2908 | 2.5827 | 1.3087 |

17 | 0.0453 | 1.1495 | 2.0482 | 1.0378 |

18 | 0.0403 | 1.0237 | 1.6243 | 0.8230 |

19 | 0.0359 | 0.9116 | 1.2881 | 0.6527 |

20 | 0.0320 | 0.8118 | 1.0215 | 0.5176 |

21 | 0.0285 | 0.7229 | 0.8101 | 0.4105 |

22 | 0.0253 | 0.6438 | 0.6424 | 0.3255 |

23 | 0.0226 | 0.5733 | 0.5095 | 0.2582 |

24 | 0.0201 | 0.5106 | 0.4040 | 0.2047 |

25 | 0.0179 | 0.4547 | 0.3204 | 0.1624 |

26 | 0.0159 | 0.4049 | 0.2541 | 0.1288 |

27 | 0.0142 | 0.3606 | 0.2015 | 0.1021 |

28 | 0.0126 | 0.3211 | 0.1598 | 0.0810 |

29 | 0.0113 | 0.2859 | 0.1267 | 0.0642 |

30 | 0.0100 | 0.2546 | 0.1005 | 0.0509 |

31 | 0.0089 | 0.2268 | 0.0797 | 0.0404 |

32 | 0.0080 | 0.2019 | 0.0632 | 0.0320 |

33 | 0.0071 | 0.1798 | 0.0501 | 0.0254 |

34 | 0.0063 | 0.1601 | 0.0398 | 0.0201 |

35 | 0.0056 | 0.1426 | 0.0315 | 0.0160 |

36 | 0.0050 | 0.1270 | 0.0250 | 0.0127 |

37 | 0.0045 | 0.1131 | 0.0198 | 0.0100 |

38 | 0.0040 | 0.1007 | 0.0157 | 0.0080 |

39 | 0.0035 | 0.0897 | 0.0125 | 0.0063 |

40 | 0.0031 | 0.0799 | 0.0099 | 0.0050 |