AWG to mm² Conversion Calculator for Solar Cable

A solar build mixes both systems whether you like it or not. Panels arrive with 4 mm² or 6 mm² leads and MC4 connectors, the charge controller manual quotes its terminals in AWG, the inverter wants "4/0 or 120 mm²", and the battery cable on the shelf is whichever the shop imports. Enter a size in either system and get the exact gauge, the copper area and the diameter, so a metric cable and an AWG cable can be compared on what actually matters: how much copper is in it.

For AWG, enter a gauge such as 10 or 4/0. For metric cable, pick mm² and enter 6.

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How It Works

Metric cable is sized by area, AWG by a drawing series

A 6 mm² cable has 6 mm² of copper in it. An AWG size does not name an area at all: it names a step in a geometric series of diameters, d = 0.005 × 92(36 - n)/39 inches for gauge n, with 1/0 to 4/0 counted as n = 0 to -3. The area follows from the diameter, so every AWG size lands on an awkward metric number, and no metric size lands exactly on a gauge. The calculator runs that series both ways and reports the exact fractional gauge, which is the honest answer, alongside the nearest whole one.

Worked example: a 6 mm² PV lead

6 mm² converts to 11,841 circular mils and a 2.76 mm solid-equivalent diameter. Running the series backwards gives an exact gauge of 9.43 AWG: between 10 and 9, nearer 9. It is nevertheless sold as "10 AWG equivalent", because 10 AWG is the next standard size down. 10 AWG is 5.26 mm², so a 10 AWG PV lead carries about 12% less copper than the 6 mm² one it stands in for. The same happens at 4 mm², which is 11.18 AWG exactly and sold as 12 AWG (3.31 mm², 17% less copper). Substituting AWG for metric always loses cross-section; substituting metric for AWG always gains it.

The conversion constant is 1 circular mil = 5.067 × 10-4 mm². Areas are for a solid conductor of the nominal diameter; the copper content of a stranded cable of the same size is the same, its outside diameter is not.

The Sizes Solar Kit Actually Comes In

UK and EU kits are metric throughout; US kit and most charge controller and inverter manuals are AWG. These are the sizes you meet on each run, with the AWG size each metric cable is sold as equivalent to, and how much copper the swap gives up.

Metric solar cable sizes with their exact AWG gauge, the AWG size they are sold as equivalent to, and the copper given up by the substitution
Where you meet it Metric cable Exact gauge Sold as That AWG's area Copper lost
PV module leads, MC4 extension cable 4 mm² 11.18 12 AWG 3.31 mm² 17%
PV module leads, MC4 extension cable 6 mm² 9.43 10 AWG 5.26 mm² 12%
Array home run to the controller 10 mm² 7.23 8 AWG 8.37 mm² 16%
Controller to battery, small banks 16 mm² 5.20 6 AWG 13.30 mm² 17%
Controller to battery, larger banks 25 mm² 3.28 4 AWG 21.15 mm² 15%
Battery to inverter, 24 V and 48 V 35 mm² 1.83 2 AWG 33.63 mm² 4%
Battery to inverter, 24 V and 48 V 50 mm² 0.29 1 AWG 42.41 mm² 15%
Battery to inverter, 12 V 70 mm² 2/0 (-1.16) 2/0 AWG 67.43 mm² 4%
Battery to inverter, 12 V, busbars 95 mm² 3/0 (-2.48) 3/0 AWG 85.03 mm² 10%

"Sold as" is the cross-reference the solar cable size calculator reports when it converts a pick between systems. Above 4/0, sizes in both systems are quoted by area (kcmil or mm²) and the gauge series stops.

MC4 connectors and the cable they fit

MC4-type connectors are supplied for a cable range, usually 2.5 to 6 mm² (14 to 10 AWG), and the crimp contact inside is matched to the cross-section and the stranding of the cable it was designed for. Cable sold as 10 AWG PV wire and cable sold as 6 mm² H1Z2Z2-K do not have the same copper area and may not have the same strand count, so the contact has to be the one specified for the cable in hand rather than the one that looks about right. Where a kit's extension leads are one system and the array leads are the other, the join is the point to check, and the calculator above tells you how far apart the two sizes really are.

Tinned fine-strand cable on boats and vans

Marine and vehicle installs use tinned, fine-stranded cable because it survives vibration and salt air, and this is where the conversion misleads people twice over. The AWG or mm² figure describes copper cross-section only. A fine-strand cable of the same nominal size has many more, thinner strands and more air between them, so its overall diameter is larger than the solid-equivalent figure the calculator gives, and lugs, glands and connector barrels are sized to the cable maker's own outside diameter, not to this chart. Electrically it behaves as its area says: a 35 mm² tinned battery cable carries the same current and drops the same voltage as any other 35 mm² copper, and the DC voltage drop calculator takes it at face value.

AWG and Metric Ampacity Side by Side

Each AWG size used in PV and battery wiring with its exact area, the metric cable it is sold against, and the allowable current of both. Copper only: aluminium is not used for module leads or battery cable.

AWG sizes with exact metric area, diameter, NEC 310.16 copper ampacity at 75 and 90 C, and the nearest metric cable with its own ampacity
AWG mm² (exact) Diameter (mm) Copper 75°C (A) Copper 90°C (A) Metric equivalent Metric 90°C (A)
14 2.08 1.63 20 25 2.5 mm² 27
12 3.31 2.05 25 30 4 mm² 36
10 5.26 2.59 35 40 6 mm² 46
8 8.37 3.26 50 55 10 mm² 63
6 13.30 4.12 65 75 16 mm² 85
4 21.15 5.19 85 95 25 mm² 112
2 33.63 6.54 115 130 35 mm² 138
1 42.41 7.35 130 145 50 mm² 168
1/0 53.47 8.25 150 170 50 mm² 168
2/0 67.43 9.27 175 195 70 mm² 213
3/0 85.03 10.40 200 225 95 mm² 258
4/0 107.22 11.68 230 260 120 mm² 299

AWG ampacities are NEC 310.16 values for not more than three current-carrying conductors at 30°C ambient; metric ampacities are the nominal IEC single-circuit values the cable size calculator uses, XLPE for the 90°C column. Neither includes the ambient or bundling derating a hot roof run needs. To size a specific run rather than compare cable, use the solar cable size calculator; to protect it, the PV fuse and breaker calculator.

Frequently Asked Questions

What size is 6 mm² solar cable in AWG?

Exactly 9.43 AWG, which is closer to 9 than to 10. It is sold as 10 AWG equivalent because 10 AWG is the next standard size down, and 10 AWG is 5.26 mm², so a 10 AWG PV lead has about 12% less copper than the 6 mm² lead it replaces. 4 mm² is 11.18 AWG and is sold as 12 AWG (3.31 mm²), giving up 17%. Going from metric to AWG always loses cross-section; going the other way always gains it.

Can I crimp MC4 connectors onto 10 AWG cable?

Only with a contact specified for it. MC4-type connectors cover a cable range, usually 2.5 to 6 mm² or 14 to 10 AWG, and the crimp contact is matched to a particular cross-section and strand construction. 10 AWG PV wire and 6 mm² H1Z2Z2-K are not the same cable, so check the connector maker's cable table for the cable you actually have rather than assuming the two are interchangeable.

What AWG is battery cable for a 12 V inverter?

Larger than most people expect, because 12 V means high current. A 2,000 W inverter at 92% efficiency draws about 181 A from a 12 V bank at nominal voltage and about 207 A at the 10.5 V low-voltage cutoff, which is the figure the cable has to be sized on. At 75°C terminations that is 4/0 AWG (107 mm²), or 120 mm² in metric cable. Run the exact inverter through the inverter sizing calculator, then the cable size calculator, rather than guessing from the chart.

Why does marine cable of the same AWG look thicker?

Because the gauge describes the copper, not the cable. Tinned fine-strand marine and vehicle cable has many more, finer strands and more air between them, so its outside diameter is bigger than the solid-conductor diameter this calculator reports. Its current rating and voltage drop are those of its cross-section like any other copper; only the lugs, glands and connector barrels need sizing to the cable maker's own outside diameter.

Does it matter if I mix AWG and mm² cable in one solar system?

Not electrically, provided each run is sized on its own actual area rather than on a "sold as" equivalence. The trap is treating 10 AWG and 6 mm² as the same cable when they differ by 12%, or fitting a lug or connector contact made for one onto the other. Convert each cable to its exact area here, size every run in the cable size calculator, and match every termination to the cable it is actually on.

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