Battery Equivalents and Replacements

AWG to mm2 Conversion Chart and Wire Sizes

copper wire 1With various standards around, it is important to know how to convert proper cable sizes from one standard to another. Also, voltage drop and power losses depend on the cable length, thickness, and current flowing through the cable.

Warning: no math in this article, seriously :)

Updated: April 1, 2022.

AWG to mm2 Conversion Chart

One of the most commonly used materials for wires is copper with the resistivity of 1.68 Ωm at 20°C. Other materials can be used as well, but most of the time, wires are made out of copper.

Keep in mind that metal resistance increases with temperature, not by much, but if you can't hold your trolling motor cables in your hands due to the heat, decrease the power and get thicker cables as soon as possible.

Chart columns:

- AWG #: American Wire Gauge cable thickness

- Diameter mm: diameter of the cable, given in millimeters. So, if you need, for example, AWG 5 cable, but you are offered cables in millimeters only, you should buy a cable 4.62 mm in diameter (with a 16.77 mm2 cross-section area), or next thicker cable.

- Diameter inches: diameter of the cable, given in inches.

- Area mm2: cross-section area of the cable, given in mm2.

- Area in2: cross-section area of the cable, given in inch2.

- Ampacity of the wires is given in Amps - Ampacity is a current-carrying capacity of the wires and is s usually defined as the maximum current that a wire can carry continuously under the conditions of use without exceeding its temperature rating.

Note: the great thing about Ampacity is that it has the same value, regardless of the voltage applied - generally, it "just" depends on the wire thickness, wire material, and quality of insulation (allowed maximum temperature).

And here is the chart:

AWG
#
Diameter
(mm)
Diameter
(inches)
Area
(mm2)
Area
(in2)
Ampacity (A)
@60°C/140°F @75°C/167°F @90°C/194°F
4/0
(0000)
11.6840 0.4600 107.2193 0.1662 195 230 260
3/0
(000)
10.4049 0.4096 85.0288 0.1318 165 200 225
2/0
(00)
9.2658 0.3648 67.4309 0.1045 145 175 195
0 8.2515 0.3249 53.4751 0.0829 125 150 170
1 7.3481 0.2893 42.4077 0.0657 110 130 145
2 6.5437 0.2576 33.6308 0.0521 95 115 130
3 5.8273 0.2294 26.6705 0.0413 85 100 115
4 5.1894 0.2043 21.1506 0.0328 70 85 95
5 4.6213 0.1819 16.7732 0.0260 - - -
AWG 6 4.1154 0.1620 13.3018 0.0206 55 65 75
7 3.6649 0.1443 10.5488 0.0164 - - -
AWG 8 3.2636 0.1285 8.3656 0.0130 40 50 55
9 2.9064 0.1144 6.6342 0.0103 - - -
AWG 10 2.5882 0.1019 5.2612 0.0082 30 35 40
11 2.3048 0.0907 4.1723 0.0065 - - -
AWG 12 2.0525 0.0808 3.3088 0.0051 20 25 30
13 1.8278 0.0720 2.6240 0.0041 - - -
AWG 14 1.6277 0.0641 2.0809 0.0032 15 20 25
15 1.4495 0.0571 1.6502 0.0026 - - -
16 1.2908 0.0508 1.3087 0.0020 - - 18
17 1.1495 0.0453 1.0378 0.0016 - - -
18 1.0237 0.0403 0.8230 0.0013 10 14 16
19 0.9116 0.0359 0.6527 0.0010 - - -
20 0.8118 0.0320 0.5176 0.0008 5 11 -
21 0.7229 0.0285 0.4105 0.0006 - - -
22 0.6438 0.0253 0.3255 0.0005 3 7 -
23 0.5733 0.0226 0.2582 0.0004 - - -
24 0.5106 0.0201 0.2047 0.0003 2.1 3.5 -
25 0.4547 0.0179 0.1624 0.0003 - - -
26 0.4049 0.0159 0.1288 0.0002 1.3 2.2 -
27 0.3606 0.0142 0.1021 0.0002 - - -
28 0.3211 0.0126 0.0810 0.0001 0.83 1.4 -
29 0.2859 0.0113 0.0642 0.0001 - - -
30 0.2546 0.0100 0.0509 0.0001 0.52 0.86 -
31 0.2268 0.0089 0.0404 0.0001 - - -
32 0.2019 0.0080 0.0320 0.0000 0.32 0.53 -
33 0.1798 0.0071 0.0254 0.0000 - - -
34 0.1601 0.0063 0.0201 0.0000 0.18 0.3 -
35 0.1426 0.0056 0.0160 0.0000 - - -
36 0.1270 0.0050 0.0127 0.0000 - - -
37 0.1131 0.0045 0.0100 0.0000 - - -
38 0.1007 0.0040 0.0080 0.0000 - - -
39 0.0897 0.0035 0.0063 0.0000 - - -
40 0.0799 0.0031 0.0050 0.0000 - - -

Personally, wires thinner than AWG20 are too thin to be used in anything except special electric and electronic projects.

Calculating the Right Wire Gauge

When looking for the right wire thickness, first we have to define the circuit maximum current and using the wire's Ampacity, find the proper wire thickness at required temperatures.

Note: 140°F (60°C) is already a hot enough temperature to prevent an adult to hold the cable with an unprotected hand for more than a few seconds. Although Ampacity value is usually calculated @167°F (75°C), using 140°F (60°C) adds an additional level of safety.

Also, for calculating wire thickness using Ampacity values, the "80% Rule" is also used.

For example, when calculating wire size for 50 Amps circuit, we will go for the wire that features Ampacity of:

Ampacity = 50 Amps / 0.80 = 62.5 Amps

Since there is no wire with an Ampacity value of 62.5 Amps, we will choose the next best thing:

- T = @60°C/140°F → Ampacity = 70 Amps → AWG 4

- T = @75°C/167°F → Ampacity = 65 Amps → AWG 6

- T = @90°C/194°F → Ampacity = 75 Amps → AWG 6

As one can see, we got two different wire thicknesses for a 50 Amps wire because three maximum temperatures were used - some electricians may consider AWG 4 wire an overkill for a 50 Amps current, especially if the wires are not extra long, but better safe than sorry. So:

50 Amps wire size → AWG 4 wire

When dimensioning circuit breakers, one must use ones recommended by the appliances that are going to be powered by the electric circuit.

However, cables can be slightly over-dimensioned, although this may lead to higher wire costs. Never, but really never use wires that are thinner than required, in this case, that would be AWG 8.

When calculating wire thickness, one also has to take into account the length of the wires by increasing the Ampacity of the wire by 10% for every 50 feet of the wire.

For more details about calculating wire thicknesses, feel free to check our articles:

Note: if You are unsure, contact a local certified electrician of a company for more information, including local laws and regulations.