6 Gauge Wire in mm: Diameter, mm2 and Ampacity

6 gauge wire measures 4.11 mm across. Its cross-section is 13.3 mm², or 26,240 circular mils.

Order 16 mm². That is 20% more copper, and it is the only sensible choice — the size below, 10 mm², is 25% less.

Ampacity

6 AWG copper carries 55 A at 60 °C, 65 A at 75 °C, and 75 A at 90 °C, for not more than three current-carrying conductors at 30 °C ambient.

The metric equivalent at 16 mm², three loaded conductors clipped direct at 30 °C:

Both systems assume three loaded conductors at 30 °C, which makes the comparison broadly fair. But they define installation methods differently and apply different derating rules, so read these as parallel answers rather than a conversion between codes.

Installation method matters more than you think

At 16 mm², the metric tables give seven different ampacities for the same cable depending on how it is installed:

That is a 36% spread between the worst and best case, for one cable. A conductor buried in insulation cannot shed heat; the same conductor clipped to a wall in free air can.

This is the number most people never look up. They find “16 mm² is 76 A,” build it into a calculation, and never notice that the 76 A assumed an installation they are not using.

What derating does to it

Take 16 mm² XLPE, clipped direct, 96 A on the table. Put it in a 40 °C plant room with two circuits bunched:

96 A × 0.91 (40 °C) × 0.80 (2 circuits) = 69.9 A

Add a third circuit and the grouping factor drops to 0.70:

96 A × 0.91 × 0.70 = 61.2 A

One extra circuit in the same bunch costs nearly 9 A. At feeder sizes, how the cables are routed frequently matters more than which cable you bought.

Routing them as a single layer on a perforated tray rather than bunched changes the three-circuit factor from 0.70 to 0.82 — recovering most of that loss for the price of a tray.

6 AWG against the 16 mm² limit

The resistance limit for 16 mm² is 1.15 Ω/km. A 6 AWG conductor measures 1.30 Ω/km, missing by 13%.

The same 13% miss appears at 12 AWG against 4 mm² and 8 AWG against 10 mm². It is not a coincidence — the AWG series and the metric series both step by a roughly constant ratio, so the mismatch repeats at similar magnitude up the range. Only where the two happen to converge, at 2 AWG and 2/0, does the conductor clear the limit. See why AWG doesn’t match metric sizes.

Conductor diameter

4.11 mm is solid wire, which you will not encounter at this size. At 16 mm²:

Class 5 at 6.3 mm is 53% wider than the solid figure. At this size that is the difference between two gland sizes. See conductor classes 1, 2, 5 and 6.

Where 6 AWG is used

Service entrance conductors on smaller services, sub-panel feeders, 60 and 65 A circuits, large motor circuits, welder outlets, and grounding electrode conductors.

It is also common on EV charger installations, where the continuous-load rules push the conductor a size above what the nameplate current alone would suggest.

FAQ

How many mm is 6 gauge wire? 4.11 mm in diameter for solid wire, which is 162.0 mils. Stranded 6 AWG measures wider.

What is 6 AWG in mm²? 13.3 mm². The metric cable size to order is 16 mm², which is 20% larger.

How many amps can 6 gauge wire carry? 55 A at 60 °C, 65 A at 75 °C, 75 A at 90 °C, before derating. Correct for ambient temperature and for how many conductors share the route.

Is 6 AWG the same as 16 mm²? No. 16 mm² has 20% more copper, and a 6 AWG conductor misses the 16 mm² resistance limit by 13%.

Can I use 10 mm² instead of 6 AWG? It has 25% less copper and carries about 57 A against the 65 A of 6 AWG at 75 °C. It is a downgrade. Check the load calculation before accepting it.

Is 6 gauge enough for a 60 amp circuit? At 75 °C, 6 AWG copper is rated 65 A before derating, so it clears 60 A with a little margin. Whether that margin survives depends on ambient temperature, conductor grouping, and the terminal ratings at both ends of the run.

Reference

Work the other direction from 16 mm² to AWG, or use the converter.