Copper Wire Resistance Calculator + Wire Resistance Chart (4/0 To 40 AWG)

Let’s say you want to calculate the wire resistance. Every wire conducts electricity but this conduction is not 100% effective. A bit of electricity is lost in the wire. How much exactly?

We will show you how to determine wire resistance manually and using the Wire Resistance Calculator below (just input the wire gauge and length of the wire to get the resistance in Ohms).

resistance in copper wires
Resistance in wires depends on specific resistivity, length, and cross-section of the wire. The Wire Resistance Calculator takes into account all 3 factors, and gives you the Ohms.

The resistance of any wire is dead simple to calculate if you just follow the formula. Here is the wire resistance formula we will use:

Table of Contents

Resistance Of Wire Formula

Resistance of any wire, be it copper, aluminum, nichrome, and so on, depends only on two primary factors. The formula for the resistance of the wire includes these two factors, expressed in this electric resistance equation, also known as Ohm’s Law formula:

R = ρ × L / A

Here is how we can read this wire resistance equation: Resistance in the wire is proportional to resistivity (denoted by the Greek letter rho or ρ) and length, and reversely proportional to the cross-section of the wire (A or area). Resistance is expressed in Ohms (denoted by the Greek letter omega or Ω); 1 Ohm is equal to V/A or volt/amp.

That simply means that:

  1. The higher the resistivity of the material wire is made out of, the higher the resistance in the wire.
  2. The longer the wire, the higher the resistance in the wire.
  3. The thicker the wire is, the lower will the resistance in the wire be.

The two primary factors we use in the wire resistance calculator (found below) are:

  1. Length of the wire. This goes without saying. A 100 feet wire will have double the resistance of a 50 feet wire.
  2. Resistivity of certain gauge wires (Example: 2 AWG, 10 AWG, 14 AWG, and so on). Here we combine the specific resistance of the material (ρ in the equation above) and the cross-section of the wire.

To illustrate what the resistivity of wires means, we have prepared a complete chart of the resistivity of copper wires from the thickest 0000 (4/0) AWG wire to the smallest 40 AWG wire. As you can see in this chart, the resistance of the thickest AWG copper wire is 0.04901 milliohms (mΩ) per foot and the resistance of the smallest AWG wire is 1049 milliohms (mΩ).

Note: 40 AWG wire has a 21,403 times higher resistance than 0000 (4/0) AWG wire because it has a 21,403 times lower thickness. This is the inverse relationship between resistance and cross-section or area.

Here is the full chart for resistivity of copper AWG wires that we will use in the wire resistance calculator:

AWG Copper Wire Resistance Chart

AWG Copper Wire: Resistance Per 1 Ft (Ohms/Ft): Resistance Per 10 Ft (Ohms/10 Ft): Resistance Per 100 Ft (Ohms/100 Ft): Resistance Per 1000 Ft (Ohms/1000 Ft):
0000 (4/0) AWG 0.04901 milliohms (mΩ) 0.4901 milliohms (mΩ) 4.901 milliohms (mΩ) 0.04901 ohms (Ω)
000 (3/0) AWG 0.06180 milliohms (mΩ) 0.6180 milliohms (mΩ) 6.180 milliohms (mΩ) 0.06180 ohms (Ω)
00 (2/0) AWG 0.07793 milliohms (mΩ) 0.7793 milliohms (mΩ) 7.793 milliohms (mΩ) 0.07793 ohms (Ω)
0 (1/0) AWG 0.09827 milliohms (mΩ) 0.9827 milliohms (mΩ) 9.827 milliohms (mΩ) 0.09827 ohms (Ω)
1 AWG 0.1239 milliohms (mΩ) 1.239 milliohms (mΩ) 12.39 milliohms (mΩ) 0.1239 ohms (Ω)
2 AWG 0.1563 milliohms (mΩ) 1.563 milliohms (mΩ) 15.63 milliohms (mΩ) 0.1563 ohms (Ω)
3 AWG 0.1970 milliohms (mΩ) 1.970 milliohms (mΩ) 19.70 milliohms (mΩ) 0.1970 ohms (Ω)
4 AWG 0.2485 milliohms (mΩ) 2.485 milliohms (mΩ) 24.85 milliohms (mΩ) 0.2485 ohms (Ω)
5 AWG 0.3133 milliohms (mΩ) 3.133 milliohms (mΩ) 31.33 milliohms (mΩ) 0.3133 ohms (Ω)
6 AWG 0.3951 milliohms (mΩ) 3.951 milliohms (mΩ) 39.51 milliohms (mΩ) 0.3951 ohms (Ω)
7 AWG 0.4982 milliohms (mΩ) 4.982 milliohms (mΩ) 49.82 milliohms (mΩ) 0.4982 ohms (Ω)
8 AWG 0.6282 milliohms (mΩ) 6.282 milliohms (mΩ) 62.82 milliohms (mΩ) 0.6282 ohms (Ω)
9 AWG 0.7921 milliohms (mΩ) 7.921 milliohms (mΩ) 79.21 milliohms (mΩ) 0.7921 ohms (Ω)
10 AWG 0.9989 milliohms (mΩ) 9.989 milliohms (mΩ) 99.89 milliohms (mΩ) 0.9989 ohms (Ω)
11 AWG 1.260 milliohms (mΩ) 12.60 milliohms (mΩ) 126.0 milliohms (mΩ) 1.260 ohms (Ω)
12 AWG 1.588 milliohms (mΩ) 15.88 milliohms (mΩ) 158.8 milliohms (mΩ) 1.588 ohms (Ω)
13 AWG 2.003 milliohms (mΩ) 20.03 milliohms (mΩ) 200.3 milliohms (mΩ) 2.003 ohms (Ω)
14 AWG 2.525 milliohms (mΩ) 25.25 milliohms (mΩ) 252.5 milliohms (mΩ) 2.525 ohms (Ω)
15 AWG 3.184 milliohms (mΩ) 31.84 milliohms (mΩ) 318.4 milliohms (mΩ) 3.184 ohms (Ω)
16 AWG 4.016 milliohms (mΩ) 40.16 milliohms (mΩ) 401.6 milliohms (mΩ) 4.016 ohms (Ω)
17 AWG 5.064 milliohms (mΩ) 50.64 milliohms (mΩ) 506.4 milliohms (mΩ) 5.064 ohms (Ω)
18 AWG 6.385 milliohms (mΩ) 63.85 milliohms (mΩ) 638.5 milliohms (mΩ) 6.385 ohms (Ω)
19 AWG 8.051 milliohms (mΩ) 80.51 milliohms (mΩ) 805.1 milliohms (mΩ) 8.051 ohms (Ω)
20 AWG 10.15 milliohms (mΩ) 101.5 milliohms (mΩ) 1015 milliohms (mΩ) 10.15 ohms (Ω)
21 AWG 12.80 milliohms (mΩ) 128.0 milliohms (mΩ) 1280 milliohms (mΩ) 12.80 ohms (Ω)
22 AWG 16.14 milliohms (mΩ) 161.4 milliohms (mΩ) 1614 milliohms (mΩ) 16.14 ohms (Ω)
23 AWG 20.36 milliohms (mΩ) 203.6 milliohms (mΩ) 2036 milliohms (mΩ) 20.36 ohms (Ω)
24 AWG 25.67 milliohms (mΩ) 256.7 milliohms (mΩ) 2567 milliohms (mΩ) 25.67 ohms (Ω)
25 AWG 32.37 milliohms (mΩ) 322.7 milliohms (mΩ) 3237 milliohms (mΩ) 32.37 ohms (Ω)
26 AWG 40.81 milliohms (mΩ) 408.1 milliohms (mΩ) 4081 milliohms (mΩ) 40.81 ohms (Ω)
27 AWG 51.47 milliohms (mΩ) 514.7 milliohms (mΩ) 5147 milliohms (mΩ) 51.47 ohms (Ω)
28 AWG 64.90 milliohms (mΩ) 649.0 milliohms (mΩ) 6490 milliohms (mΩ) 64.90 ohms (Ω)
29 AWG 81.84 milliohms (mΩ) 818.4 milliohms (mΩ) 8184 milliohms (mΩ) 81.84 ohms (Ω)
30 AWG 103.2 milliohms (mΩ) 1032 milliohms (mΩ) 10320 milliohms (mΩ) 103.2 ohms (Ω)
31 AWG 130.1 milliohms (mΩ) 1301 milliohms (mΩ) 13010 milliohms (mΩ) 130.1 ohms (Ω)
32 AWG 164.1 milliohms (mΩ) 1641 milliohms (mΩ) 16410 milliohms (mΩ) 164.1 ohms (Ω)
33 AWG 206.9 milliohms (mΩ) 2069 milliohms (mΩ) 20690 milliohms (mΩ) 206.9 ohms (Ω)
34 AWG 260.9 milliohms (mΩ) 2609 milliohms (mΩ) 26090 milliohms (mΩ) 260.9 ohms (Ω)
35 AWG 329.0 milliohms (mΩ) 3290 milliohms (mΩ) 32900 milliohms (mΩ) 329.0 ohms (Ω)
36 AWG 414.8 milliohms (mΩ) 4148 milliohms (mΩ) 41480 milliohms (mΩ) 414.8 ohms (Ω)
37 AWG 523.1 milliohms (mΩ) 5231 milliohms (mΩ) 52310 milliohms (mΩ) 523.1 ohms (Ω)
38 AWG 659.6 milliohms (mΩ) 6596 milliohms (mΩ) 65960 milliohms (mΩ) 659.6 ohms (Ω)
39 AWG 831.8 milliohms (mΩ) 8318 milliohms (mΩ) 83180 milliohms (mΩ) 831.8 ohms (Ω)
40 AWG 1049 milliohms (mΩ) 10490 milliohms (mΩ) 104900 milliohms (mΩ) 1049 ohms (Ω)

Wire Resistance Calculator

First of, pick the length of the wire. Secondly, just choose the AWG wire you are using and the calculator will automatically calculate how much resistance is in that wire:


As an example, let’s look at a 100 feet long 14 AWG wire. If you slide the first slider to ‘100’ and choose the ’14 AWG’ wire, the resistance calculator will tell you that such a wire has a total resistance of 0.25250 Ohms (Ω).

You can choose any AWG wire and do this calculation. Here is how you can manually get the same result:

How To Calculate The Resistance Of The Wire?

We will be using the formula for the resistivity of the wire above. Let’s say we have a 150 feet long 10 AWG copper wire. How much resistance is in this 10 AWG wire?

R = ρ × L / A

In this equation we know that the length (L) is 150 feet. ρ and A (or ρ/A) can be read from the AWG resistivity chart; it’s 0.9989 milliohms (mΩ) per foot or 0.0009989 ohms (Ω) per foot. We simply put both things in the wire resistance equation like this:

R (150 ft 10 AWG wire) = 0.0009989 ohms/ft × 150 ft = 0.14984 Ohms

If you the same calculation with the wire resistivity calculator above, you get the same result: A 150 ft 10 AWG copper wire has a resistance of 0.14984 Ohms (Ω).

Hopefully, now you know how to use the length of wire and resistance formula to calculate the resistance in any wire. If you don’t find your answer here, you can use the comment section below and we’ll try to help you out.

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