# Wire Gauge Charts: AWG to mm2 Conversion Charts and Wire Sizes

With 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.

Updated: March 21, 2023.

## AWG to mm2 Conversion Chart

Some of the most commonly used materials for wires are copper, with a resistivity of pure copper of 16.78 nΩm at 20°C and aluminum, with a resistivity of pure aluminum of 26.5 nΩm at 20°C. Other materials can be used as well, but most of the time, wires are made out of these materials.

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 the 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 Ampacity chart of enclosed copper wires:

 AWG# Diameter(mm/inches) Area(mm2/in2) Resistance (Copper)(mΩ/m;mΩ/ft) Ampacity (A) @60°C/140°F @75°C/167°F @90°C/194°F 4/0(0000) 11.68400.4600 107.21930.1662 0.16080.04901 195 230 260 3/0(000) 10.40490.4096 85.02880.1318 0.20280.06180 165 200 225 2/0(00) 9.26580.3648 67.43090.1045 0.25570.07793 145 175 195 AWG 0 (1/0) 8.25150.3249 53.47510.0829 0.32240.09827 125 150 170 1 7.34810.2893 42.40770.0657 0.40660.1239 110 130 145 2 6.54370.2576 33.63080.0521 0.51270.1563 95 115 130 3 5.82730.2294 26.67050.0413 0.64650.1970 85 100 115 AWG 4 5.18940.2043 21.15060.0328 0.81520.2485 70 85 95 5 4.62130.1819 16.77320.0260 1.0280.3133 - - - AWG 6 4.11540.1620 13.30180.0206 1.2960.3951 55 65 75 7 3.66490.1443 10.54880.0164 1.6340.4982 - - - AWG 8 3.26360.1285 8.36560.0130 2.0610.6282 40 50 55 9 2.90640.1144 6.63420.0103 2.5990.7921 - - - AWG 10 2.58820.1019 5.26120.0082 3.2770.9989 30 35 40 11 2.30480.0907 4.17230.0065 4.1321.260 - - - AWG 12 2.05250.0808 3.30880.0051 5.2111.588 20 25 30 13 1.82780.0720 2.62400.0041 6.5712.003 - - - AWG 14 1.62770.0641 2.08090.0032 8.2862.525 15 20 25 15 1.44950.0571 1.65020.0026 10.453.184 - - - 16 1.29080.0508 1.30870.0020 13.174.016 - - 18 17 1.14950.0453 1.03780.0016 16.615.064 - - - AWG 18 1.02370.0403 0.82300.0013 20.956.385 10 14 16 19 0.91160.0359 0.65270.0010 26.428.051 - - - 20 0.81180.0320 0.51760.0008 33.3110.15 5 11 - 21 0.72290.0285 0.41050.0006 42.0012.80 - - - 22 0.64380.0253 0.32550.0005 52.9616.14 3 7 - 23 0.57330.0226 0.25820.0004 66.7920.36 - - - 24 0.51060.0201 0.20470.0003 84.2225.67 2.1 3.5 - 25 0.45470.0179 0.16240.0003 106.232.37 - - - 26 0.40490.0159 0.12880.0002 133.940.81 1.3 2.2 - 27 0.36060.0142 0.10210.0002 168.951.47 - - - 28 0.32110.0126 0.08100.0001 212.964.90 0.83 1.4 - 29 0.28590.0113 0.06420.0001 268.581.84 - - - 30 0.25460.0100 0.05090.0001 338.6103.2 0.52 0.86 - 31 0.22680.0089 0.04040.0001 426.9130.1 - - - 32 0.20190.0080 0.03200.0000 538.3164.1 0.32 0.53 - 33 0.17980.0071 0.02540.0000 678.8206.9 - - - 34 0.16010.0063 0.02010.0000 856.0260.9 0.18 0.3 - 35 0.14260.0056 0.01600.0000 1079329.0 - - - 36 0.12700.0050 0.01270.0000 1361414.8 - - - 37 0.11310.0045 0.01000.0000 1716523.1 - - - 38 0.10070.0040 0.00800.0000 2164659.6 - - - 39 0.08970.0035 0.00630.0000 2729831.8 - - - 40 0.07990.0031 0.00500.0000 34411049 - - -

Note: Ampacities are given for enclosed wires @86°F (@30°C) ambient temperatures.

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

## Wire Thickness: Circular Mil (kcmil) vs. mm2

A circular mil equals the area of a circle with a diameter of one-thousandth of an inch (one mil) or 0.0254 mm and it has a value of 5.067075×10−4 mm2 (506.7075 μm2).

In Canada and the United States, circular mils (cmil) are used to define wire sizes larger than 0000 AWG (4/0 AWG), starting with 250000 cmil, which is written as 250 kcmil or 250 MCM - 250 thousand circular mil.

Standard wire sizes are from:

• from 250 to 400 in increments of 50 kcmil,
• from 400 to 1000 in increments of 100 kcmil,
• from 1000 to 2000 in increments of 250 kcmil.

The following chart lists solid insulated copper wire Ampacities for wire areas given in kcmil and mm2 and wire diameters given in mm2 and inch2.

 Areakcmil (MCM); mm2 Wire Diameterinches; mm Insulated Solid Copper Wire Ampacity (A) Insulated Solid Aluminum Wire Ampacity (A) @60°C/140°F @75°C/167°F @90°C/194°F @60°C/140°F @75°C/167°F @90°C/194°F 250126.7 0.50012.70 215 255 290 170 205 230 300152.0 0.54813.91 240 285 320 190 230 255 350177.3 0.59215.03 260 310 350 210 250 280 400 kcmil Wire202.7 0.63216.06 280 335 380 225 270 305 500 kcmil Wire253.4 0.70717.96 320 380 430 260 310 350 600304.0 0.77519.67 355 420 475 285 340 385 700354.7 0.83721.25 385 460 520 310 375 420 750380.0 0.86622.00 400 475 535 320 385 435 800405.4 0.89422.72 410 490 555 330 395 450 900456.0 0.94924.10 435 520 585 355 425 480 1000506.7 1.00025.40 455 545 615 375 445 500 1250633.4 1.11828.40 495 590 665 405 485 545 1500760.1 1.22531.11 520 625 705 435 520 585 1750886.7 1.32333.60 545 650 735 455 545 615 20001013.4 1.41435.92 560 665 750 470 560 630

Note: stranded copper wires have a diameter 5-7% larger to compensate for gaps between the wire strands and must be checked for each wire.

## Ampacities of Wires in Free Air

Wires, cables, and conductors, in general, have higher ampacities when suspended in air due to better cooling. This cooling effect can be even increased when, for example, powering an electric trolling motor and a gentle breeze sweeps across the lake, river, or sea surface.

However, wires suspended freely in the air can also be heated by, for example, the sun. Thus, use these values as such, but when in doubt, always go for thicker wires and keep them protected from the sun and similar heat sources.

 Wire Size(AWG or kcmil) Ampacity (Copper Wire) Ampacity (Aluminum Wire) 60°C(140°F) 75°C(167°F) 90°C(194°F) 60°C(140°F) 75°C(167°F) 90°C(194°F) AWG 14 Wire 25 30 35 – – – AWG 12 Wire 30 35 40 25 30 35 AWG 10 Wire 40 50 55 35 40 40 AWG 8 Wire 60 70 80 45 55 60 AWG 6 Wire 80 95 105 60 75 80 AWG 4 Wire 105 125 140 80 100 110 3 120 145 165 95 115 130 2 140 170 190 110 135 150 1 165 195 220 130 155 175 AWG 1/0 Wire 195 230 260 150 180 205 2/0 225 265 300 175 210 235 3/0 260 310 350 200 240 275 4/0 300 360 405 235 280 315 250 340 405 455 265 315 355 300 375 445 505 290 350 395 350 420 505 570 330 395 445 400 kcmil Wire 455 545 615 355 425 480 500 kcmil Wire 515 620 700 405 485 545 600 575 690 780 455 540 615 700 630 755 855 500 595 675 750 655 785 885 515 620 700 800 680 815 920 535 645 725 900 730 870 985 580 700 785 1000 780 935 1055 625 750 845 1250 890 1065 1200 710 855 960 1500 980 1175 1325 795 950 1075 1750 1070 1280 1445 875 1050 1185 2000 1155 1385 1560 960 1150 1335

Types:

• 60°C (140°F): TW, UF,
• 75°C (167°F): RHW, THHW, THW, THWN, XHHW, ZW,
• 90°C (194°F): FEP, FEPB, MI, RHH, RHW-2, SA, SIS, TBS, THHN, THHW, THW-2, THWN-2, USE-2, XHH, XHHW, XHHW-2, ZW-2.

## 12V Wire Gauge Chart

12V voltage is the standard voltage used in cars, trucks, boats, campers, etc., and is equivalent to the nominal voltage of a 6-cell lead-acid battery.

To transfer energy efficiently, wires must be thick enough to keep energy losses to a minimum. Too thick wires can be used, but thick wires are more difficult to work with (even when stranded wires are used), they are heavier and more expensive.

The standard acceptable voltage drop in 12V circuits is 3%, which is 0.36 volts.

Thus, the total resistance of the wire can be calculated as follows:

R (Ω) = U(V) / I(A) = 0.36V / I(A)

where I(A) is the maximum current through the wire.

Note: since cables generally have two wires, if You need a cable that is 10 feet long, calculate the total resistance for 20 feet long wire.

 American Wire Gauge (#AWG) Copper Wires Suspended In Air Length Maximum Current (Amps) @12V (Max. 0.36V Voltage Drop) 1 5 10 15 20 25 30 40 50 60 70 10ft; 3.05m 24 18 14 12 12 10 10 8 6 6 4 15ft; 4.57m 22 16 12 10 10 8 8 6 6 4 4 20ft; 6.1m 22 14 12 10 8 8 6 6 4 4 4 25ft; 7.62m 20 14 10 8 8 6 6 4 4 2 2 30ft; 9.15m 20 12 10 8 6 6 4 4 2 2 2 40ft; 12.2m 18 12 8 6 6 4 4 2 2 1 1/0 50ft; 15.2m 18 10 8 6 4 4 2 2 1 1/0 1/0 60ft; 18.3m 16 10 6 6 4 2 2 1 1/0 2/0 2/0 70ft; 21.3m 16 10 6 4 2 2 2 1/0 2/0 2/0 3/0 80ft; 24.4m 16 8 6 4 2 2 1 1/0 2/0 3/0 3/0 90ft; 27.4m 14 8 4 4 2 1 1/0 2/0 3/0 3/0 4/0 100ft; 30.5m 14 8 4 2 2 1 1/0 2/0 3/0 4/0 4/0

Note: for the values that were very close, the thicker wire was chosen. Also, the actual Ampacity (80% of theoretical Ampacity) of wires suspended in the air was taken into account.

## Calculating the Right Wire Gauge

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

Note: 140°F (60°C) is already a hot enough temperature to prevent an adult from holding the cable with an unprotected hand for more than a few seconds.

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 an 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

Note: these are values for "enclosed" wires. Due to additional cooling of air-suspended wires, their Ampacities are higher.

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 the 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 consider the length of the wires by increasing the required 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.

## How To Calculate Wire Resistance

Wire resistance is very simple to calculate using wire thickness, length, and material.

For example, we want to calculate the electric resistance of a two-wire, 6-gauge, 10 feet long, cable.

R (Ω) = 20 feet * 0.3951 mΩ/feet = 7.902 mΩ

Note: two-wire 10 feet long cable has 20 feet of wire, hence, we multiply with 20 feet and not with 10 feet.

So, a two-wire, the 6-gauge cable features electric resistance of 7.902 mΩ, or 7.902 * 10-3 Ω, or 0.007902 Ω.

Another example:

For example, if we have 6 gauge wire which is 3 meters long, its resistance is:

R = (1.296 mΩ/m) * 3m = 3.888 mΩ

which is a very simple thing to do.

But, if we want to calculate the wire resistance of the same wire using copper specific electrical resistance of 16.78 nΩm, we get:

R = (16.78 nΩm * 3m) / 13.3018 mm2 = 3.78445 mΩ

So, we get two different values - the question is, why?

Wire resistance values in the chart are given for real-life copper wire, which always has some impurities, while copper specific electrical resistance of 16.78 nΩm is given for pure copper.

So, for real-life wires, always use values from the chart, or use real-life copper relative resistance of ~17.24 nΩm (instead of 16.78 nΩm), or simply go for a somewhat thicker wire.

## How To Calculate Wire Energy Losses

Energy losses should be kept to a minimum for many reasons, including lower electric bills and decreased danger of wire overheating or even wire fire.

To calculate energy losses and voltage drops, we use the following formulas:

U(V) = I(A) * R(Ω)

P(W) = U(V) * I(A) = I(A)2 * R(Ω) = U(V)2 / R(Ω)

E(J) = P(W) * t(s)

For example, we want to calculate energy losses and voltage drop for an electric trolling motor with the following features:

• maximum current draw: 50 Amps
• voltage: 12V
• cable: 5ft 6 gauge cable or 5ft 8 gauge cable (10ft total wire length, wires are free in the air)

If we check the charts, we can calculate the voltage drop in the cable:

• 8 gauge wire: 0.6282 mΩ/ft → U(V) = 314.1 mV
• 6 gauge wire: 0.3951 mΩ/ft → U(V) = 197.55 mV

In order to keep energy losses to 3% or lower, the maximum voltage drop should be:

Umax.drop(V) = 12V * 0.03 = 0.36V = 360 mV

Thus, both 8 gauge and 6 gauge wires satisfy this requirement and as such can be used for powering an electric trolling motor in this example.

Also, power losses are:

• 8 gauge wire: Ploss-8-gauge(W) = 0.3141V * 50A = 15.7W
• 6 gauge wire: Ploss-6-gauge(W) = 0.19755V * 50A = 9.8775W
• total power: Ptot(W) = 12V * 50A = 600W

As one can see, the power loss difference between 8 gauge and 6 gauge wire in this example is "just" ~6 Watts, which is "only" 1% of total battery power.

Note: 6 gauge wire features a diameter of 4.1154mm, and 8 gauge wire features a diameter of 3.2636mm - nice braided 6 gauge wire is just as easily worked with as nice braided 8 gauge wire and can withstand much more. Fortunately, electric trolling motors are rarely pushed at 100% throttle, generally keeping their wires relatively cold. And if You push your trolling motor at 100% throttle almost all the time, your electric trolling motor is seriously underpowered.

However, theoretical Ampacities for solid copper 8 gauge and 6 gauge wires is 60 Amps and 80 Amps respectively, which after applying 80% Rule drops down to 48 Amps and 72 Amps. Thus, for 10 feet long wire (5 feet cable) that must support real 50 Amps, one should go for 6 gauge wire, not 8 gauge wire.