Online Calculators & Tools




Voltage Drop Conversion Calculator

Wire / cable voltage drop calculator and how to calculate.



Wire type:  
 
Resistivity: Ω·m
 
Wire diameter size:
 
Wire/cable length (one way):
 
Current type:
 
Voltage in volts: V
 
Current in amps: A
 
 
 
Voltage drop in volts: V
 
Percentage of voltage drop: %
 
Wire resistance: Ω



Voltage drop calculations and chart

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:

Vdrop (V) = Iwire (A) × Rwire(Ω)

= Iwire (A) × (2 × L(ft) × Rwire(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:

Vdrop (V) = Iwire (A) × Rwire(Ω)

= Iwire (A) × (2 × L(m) × Rwire (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:

Vdrop (V) = √3 × Iwire (A) × Rwire (Ω)

= 1.732 × Iwire (A) × (L(ft) × Rwire (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:

Vdrop (V) = √3 × Iwire (A) × Rwire (Ω)

= 1.732 × Iwire (A) × (L(m) × Rwire (Ω/km) / 1000(m/km))

Wire diameter calculations

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

dn (in) = 0.005 in × 92(36-n)/39

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

dn (mm) = 0.127 mm × 92(36-n)/39

Wire cross sectional area calculations

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

An (kcmil) = 1000×dn2 = 0.025 in2 × 92(36-n)/19.5

The n gauge wire's cross sercional area An in square inches (in2) is equal to pi divided by 4 times the square wire diameter d in inches (in):

An (in2) = (π/4)×dn2 = 0.000019635 in2 × 92(36-n)/19.5

The n gauge wire's cross sercional area An in square millimeters (mm2) is equal to pi divided by 4 times the square wire diameter d in millimeters (mm):

An (mm2) = (π/4)×dn2 = 0.012668 mm2 × 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 25.42 times the cross sectional area An in square inches (in2):

Rn (Ω/kft) = 0.3048 × 109 × ρ(Ω·m) / (25.42 × An (in2))

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 An in square millimeters (mm2):

Rn (Ω/km) = 109 × ρ(Ω·m) / An (mm2)


How to calculate voltage drop:

Multiply current in amperes by the length of the circuit in feet to get ampere-feet. Circuit length is the distance from the point of origin to the load end of the circuit. Divide by 100. ... Result is voltage drop.


voltage-drop-formula

AWG chart

AWG Diameter Turns of wire Area Copper resistance
inch mm per inch per cm kcmil mm2 Ω/km Ω/1000ft
0000 (4/0) 0.4600 11.684 2.17 0.856 212 107 0.1608 0.04901
000 (3/0) 0.4096 10.404 2.44 0.961 168 85.0 0.2028 0.06180
00 (2/0) 0.3648 9.266 2.74 1.08 133 67.4 0.2557 0.07793
0 (1/0) 0.3249 8.252 3.08 1.21 106 53.5 0.3224 0.09827
1 0.2893 7.348 3.46 1.36 83.7 42.4 0.4066 0.1239
2 0.2576 6.544 3.88 1.53 66.4 33.6 0.5127 0.1563
3 0.2294 5.827 4.36 1.72 52.6 26.7 0.6465 0.1970
4 0.2043 5.189 4.89 1.93 41.7 21.2 0.8152 0.2485
5 0.1819 4.621 5.50 2.16 33.1 16.8 1.028 0.3133
6 0.1620 4.115 6.17 2.43 26.3 13.3 1.296 0.3951
7 0.1443 3.665 6.93 2.73 20.8 10.5 1.634 0.4982
8 0.1285 3.264 7.78 3.06 16.5 8.37 2.061 0.6282
9 0.1144 2.906 8.74 3.44 13.1 6.63 2.599 0.7921
10 0.1019 2.588 9.81 3.86 10.4 5.26 3.277 0.9989
11 0.0907 2.305 11.0 4.34 8.23 4.17 4.132 1.260
12 0.0808 2.053 12.4 4.87 6.53 3.31 5.211 1.588
13 0.0720 1.828 13.9 5.47 5.18 2.62 6.571 2.003
14 0.0641 1.628 15.6 6.14 4.11 2.08 8.286 2.525
15 0.0571 1.450 17.5 6.90 3.26 1.65 10.45 3.184
16 0.0508 1.291 19.7 7.75 2.58 1.31 13.17 4.016
17 0.0453 1.150 22.1 8.70 2.05 1.04 16.61 5.064
18 0.0403 1.024 24.8 9.77 1.62 0.823 20.95 6.385
19 0.0359 0.912 27.9 11.0 1.29 0.653 26.42 8.051
20 0.0320 0.812 31.3 12.3 1.02 0.518 33.31 10.15
21 0.0285 0.723 35.1 13.8 0.810 0.410 42.00 12.80
22 0.0253 0.644 39.5 15.5 0.642 0.326 52.96 16.14
23 0.0226 0.573 44.3 17.4 0.509 0.258 66.79 20.36
24 0.0201 0.511 49.7 19.6 0.404 0.205 84.22 25.67
25 0.0179 0.455 55.9 22.0 0.320 0.162 106.2 32.37
26 0.0159 0.405 62.7 24.7 0.254 0.129 133.9 40.81
27 0.0142 0.361 70.4 27.7 0.202 0.102 168.9 51.47
28 0.0126 0.321 79.1 31.1 0.160 0.0810 212.9 64.90
29 0.0113 0.286 88.8 35.0 0.127 0.0642 268.5 81.84
30 0.0100 0.255 99.7 39.3 0.101 0.0509 338.6 103.2
31 0.00893 0.227 112 44.1 0.0797 0.0404 426.9 130.1
32 0.00795 0.202 126 49.5 0.0632 0.0320 538.3 164.1
33 0.00708 0.180 141 55.6 0.0501 0.0254 678.8 206.9
34 0.00630 0.160 159 62.4 0.0398 0.0201 856.0 260.9
35 0.00561 0.143 178 70.1 0.0315 0.0160 1079 329.0
36 0.00500 0.127 200 78.7 0.0250 0.0127 1361 414.8
37 0.00445 0.113 225 88.4 0.0198 0.0100 1716 523.1
38 0.00397 0.101 252 99.3 0.0157 0.00797 2164 659.6
39 0.00353 0.0897 283 111 0.0125 0.00632 2729 831.8
40 0.00314 0.0799 318 125 0.00989 0.00501 3441 1049