Voltage Drop Calculator

Wire / cable voltage drop calculator and how to calculate.

• Voltage drop calculator
• Voltage drop calculations

Voltage drop calculator

Wire type:	-- select -- Copper Aluminum Carbon steel Electrical steel Gold Nichrome Nickel Silver
Resistivity:		Ω·m
Wire diameter size:		AWG inch mm
Wire/cable length (one way):		feet meters
Current type:	DC AC - Single phase AC - Three phase
Voltage in volts:		V
Current in amps:		A
Voltage drop in volts:		V
Percentage of voltage drop:		%
Wire resistance:		Ω

* @ 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.

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Voltage drop calculations

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_n² = 0.025 in² × 92^(36-n)/19.5

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

A_{n (in}2₎ = (π/4)×d_n² = 0.000019635 in² × 92^(36-n)/19.5

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

A_{n (mm}2₎ = (π/4)×d_n² = 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 A_n in square inches (in²):

R_{n (Ω/kft)} = 0.3048 × 10⁹ × ρ_(Ω·m) / (25.4² × 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 (mm²):

R_{n (Ω/km)} = 10⁹ × ρ_(Ω·m) / A_{n (mm}2₎

AWG chart

AWG #	Diameter (inch)	Diameter (mm)	Area (kcmil)	Area (mm2)
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

In Physics, the voltage drop is defined as the amount of voltage drop/loss occurs as a part of the circuit or through all the circuit due to the impedance. Usually, the voltage drop happens due to the increased resistance in the circuit. Other causes of voltage drop may be due to extra components, connections or the high-resistance conductors, increased load and so on.

It is a conversion calculator used to convert the values in Standard wire gauge (SWG) to millimeters (mm) and square millimeters (mm2). It is simple to use as it only has a single text field where you will select the gauge number. Click the down arrow on the right side of the ‘select SWG’ to give you the options. Once you have chosen the appropriate value, click the ‘Calculate’ button to execute the conversion.

This calculator also has the ‘Reset’ button which performs a different function. It is used to erase all data of the previous calculations. It is the fastest way of clearing the text fields whenever you want to perform new conversions. The results will be displayed below the two controls. You can determine the Diameter in millimeters, Diameter in inches and the Cross sectional area in square millimeters.

Formula of calculating the wire cross sectional area An (mm2) = (∏/4) x dn2, which means that the n gauge wire’s cross sectional area in square millimeters is computed by multiplying the square wire diameter in millimeters by pi divided by 4.

For example,

If the Standard wire gauge is 47 (SWG), what are the Diameter in millimeters, square millimeters and inches?

Solution

The first procedure will be to select the gauge number 47 in the first text field. Click the Calculate button to execute a quick conversion. Your results will be displayed as;

Diameter in millimeters = 0.051 (mm)

Diameter in Inches = 0.002 (inches)

Cross sectional area in square millimeters = 0.0020 (mm2)

If you wish to carry out new conversions from SWG to mm, use the ‘Reset’ button to clear the text fields at once. You can then select the gauge number and perform the same procedure to acquire your results in millimeters, inches and square millimeters. It is also important to know that this calculator only deals with conversions from SWG to mm and not the reverse. You can always coordinate the two controls to perform several calculations within a short period.