Voltage Drop Calculator

voltage drop calculator

Please select current type from drop-down list and Input the Resistivity,wire diameter size,wire length,select current type from drop-down list ,input the current and volts(V) and click the calculate button for the result. 
In this Post We will Cover following topics 3 phase voltage drop calculation example,3 phase voltage drop calculation formula,how to compute voltage drop of 3 phase power cable,3 phase voltage drop calculator.

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


Online Voltage drop calculations

How to calculate Voltage drop in DC / single phase calculation
Vdrop (V) = Iwire (A) × Rwire(Ω)
= Iwire (A) × (2 × L(ft) × Rwire(Ω/kft) / 1000(ft/kft))

Vdrop (V)=voltage drop V in volts (V)
Iwire (A)=wire current I in amps (A)
L(ft)= wire length L in feet (ft)
Rwire(Ω)=R in ohms (Ω/kft)
How to calculate Voltage drop 3 phase(If wire length in meters)

Vdrop (V) = Iwire (A) × Rwire(Ω)
= Iwire (A) × (2 × L(m) × Rwire (Ω/km) / 1000(m/km))

Vdrop (V)=voltage drop V in volts (V)
Iwire (A)=wire current I in amps (A)
L(m)= wire length L in meters (m)
Rwire(Ω)= R in ohms (Ω/km)

How to calculate Voltage drop 3 phase(wire length L in feet (ft))
Vdrop (V) = √3 × Iwire (A) × Rwire (Ω)
= 1.732 × Iwire (A) × (L(ft) × Rwire (Ω/kft) / 1000(ft/kft))

Vdrop (V)=voltage drop V in volts (V)
Iwire (A)=wire current I in amps (A)
L(ft)= wire length L in feet (ft)
Rwire(Ω)=R in ohms (Ω/kft)


How to calculate Voltage drop 3 phase(wire length L in meters(m))
Vdrop (V) = √3 × Iwire (A) × Rwire (Ω)
= 1.732 × Iwire (A) × (L(m) × Rwire (Ω/km) / 1000(m/km))

Vdrop (V)=voltage drop V in volts (V)
Iwire (A)=wire current I in amps (A)
L(m)= wire length L in meters (m)
Rwire(Ω)= R in ohms (Ω/km)

How To calculate Wire diameter (if gauge wire diameter dm in inches)

If gauge wire diameter dm in inches
dk(in) = 0.005 in × 92(36-k)/39

How To calculate Wire diameter (if gauge wire diameter dm in millimeters)

dk(mm) = 0.005 mm × 92(36-k)/39

How to calculate Wire cross sectional area (in kcmil)

Ak (kcmil) = 1000×dk2 = 0.025 in2 × 92(36-k)/19.5
An=cross sectional area in kilo-circular mils
dn=wire diameter d in inches

How to calculate Wire cross sectional area (in inches) 

Ak (in2) = (π/4)×dk2 = 0.000019635 in2 × 92(36-k)/19.5
An=cross sectional area in inches
dn=wire diameter d in inches

How to calculate Wire cross sectional area (in millimeters)

Ak(mm2) = (π/4)×dk2 = 0.012668 mm2 × 92(36-k)/19.5

An=cross sectional area in millimeters
dn=wire diameter d in  millimeters

How to calculate Wire resistance (per kilofeet)

Rk (Ω/kft) = 0.3048 × 109 × ρ(Ω·m) / (25.42 × Ak (in2))
 R=resistance in ohms per kilofeet (Ω/kft)
 ρ =wire's resistivity in ohm-meters (Ω·m)
 An=cross sectional area An in square millimeters (mm2)

How to calculate Wire resistance (per  kilometer)

R(Ω/km) = 109 × ρ(Ω·m) / Ak (mm2)
R=resistance in ohms per kilometer (Ω/km)
ρ =wire's resistivity  in ohm-meters (Ω·m)
Ak=cross sectional area An in square millimeters (mm2)


Lets take example
I have three resistors R1,R2 and R3,All resistors connected in series with 10 volt battery
Lets take  R1 =10 ohms, R2 = 20 ohms,R2 = 30 ohms.
So that sum of resistance in the circuit is R1+R2+r3 = 10+20+30= 60 ohms.
apply ohm’s law so that we can compute the current flow from the 10 battery across All resistors (R1,R2 and R3).
All resistors  are connected in series so that the current flow across All resistors
wil be the same. According to
Ohm’s law Voltage= (I)*(R)

V= IR => I=V/R

I= 10V/60 Ohms= 0.17 amps so that the current flowing across All resistors is 0.17 amps.

Now we know that current flow across All is 0.17 amps so that we can caculate voltage drop
through each resistor using ohm’s law.
Voltage drop through R1 is V= (0.17 amps)x(10 ohms) = 1.7volts
Voltage drop through R2 is V=(0.17 amps)x(20 oms) = 3.4 volts
Voltage drop through R3 is V=(0.17 amps)x(30 oms) = 5.1 volts
The total voltage is equal to battery voltage = voltage drop through R1+voltage drop through R2+voltage drop through R3
total voltage = 1.7V+3.4V+5.1V= 5V.

All wires with long length can be serve as resistors in the circuit and So that you can calculate voltage drop through as above. Producer of the wire generally specs the wire as resistance per for feet or  per meters.complete resistance of the cable can be computed based on the length of  the cable.if your cable or wire length is less them 50 ft then you don't have to worry about the resistance

AWG wire Chart


AWG wire diameter dn Turns of wire Area Unit Copper resistance Unit
inch mm per inch per cm kcmil mm2 O/km O/kFT
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
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
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
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

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