10 mm² converts to 7 AWG by cross-sectional area. 7 AWG is 10.6 mm², only 6% larger, and it meets the resistance limit.
It is also a gauge you will not buy, and one that does not appear in the ampacity tables at all.
The gauge that exists on paper only
7 AWG is defined in the wire gauge standard. It has a diameter, an area, and a resistance. What it does not have is a row in the ampacity table — that table jumps straight from 8 AWG to 6 AWG.
So even if you found a drum of it, you would have no published current rating to size the circuit from.
That makes this a two-option decision in practice:
| Option | Cross-section | Against 10 mm² | Resistance | Limit 1.83 Ω/km |
|---|---|---|---|---|
| 8 AWG | 8.37 mm² | −16% | 2.06 Ω/km | fails by 13% |
| 7 AWG | 10.6 mm² | +6% | 1.63 Ω/km | passes |
| 6 AWG | 13.3 mm² | +33% | 1.30 Ω/km | passes |
6 AWG is the safe substitute. It overshoots by a third, but it meets the conductor resistance requirement and it is stocked everywhere.
8 AWG is 16% under and misses the resistance limit by 13%. It carries 50 A at 75 °C against the 57 A of 10 mm² clipped direct.
When 8 AWG is defensible
Worth being honest about this, because 6 AWG is a noticeably heavier cable to pull, terminate and pay for.
If you are meeting a written specification that calls for 10 mm² conductor resistance, 8 AWG fails and there is no argument to make. Take 6 AWG.
If you are matching an existing metric design on a working installation, run the numbers for the actual route. 10 mm² circuits are frequently designed with margin, and 8 AWG at 50 A may clear the load comfortably. That is a legitimate engineering decision rather than a shortcut — but make it deliberately, and write down that you checked.
The one case where 8 AWG is clearly wrong is a long run. At 2.06 Ω/km against 1.30 for 6 AWG, the voltage drop over distance is 58% higher, and that is usually why 10 mm² was specified in the first place.
Ampacity
Three loaded conductors clipped direct at 30 °C:
| Insulation | 10 mm² | 8 AWG | 6 AWG |
|---|---|---|---|
| PVC / 70–75 °C | 57 A | 50 A | 65 A |
| XLPE / 90 °C | 71 A | 55 A | 75 A |
All before derating. Take 10 mm² PVC at 57 A in a 45 °C plant room with four circuits bunched together:
57 A × 0.79 (45 °C) × 0.65 (4 circuits) = 29.3 AThe 57 A conductor is a 29 A conductor in that installation. Grouping does more damage than temperature here — four bunched circuits alone costs 35%. Routing them as a single layer on a perforated tray instead changes the factor from 0.65 to 0.77.
Conductor diameter
A solid conductor of 10 mm² works out to 3.568 mm across. At this size you are buying stranded.
| Construction | Max diameter | Min strands | Max strand dia. |
|---|---|---|---|
| Class 1, solid | 3.7 mm | 1 | — |
| Class 2, stranded | 4.2 mm | 7 | — |
| Class 5, flexible | 5.1 mm | — | 0.41 mm |
| Class 6, very flexible | 5.1 mm | — | 0.21 mm |
Solid 8 AWG is 3.26 mm and solid 6 AWG is 4.11 mm.
Class 5 at 5.1 mm is 38% wider than the class 1 maximum, which is a gland size. Note also the strand fineness — 0.41 mm for class 5 against 0.21 mm for class 6. If the cable feeds anything that moves, that difference is what decides whether it survives. See conductor classes 1, 2, 5 and 6.
Where 10 mm² is used
Cooker and shower circuits, sub-main runs, larger motor supplies, EV charge points, solar PV string and array cable, and main earthing conductors on smaller services.
In PV work it is particularly common because array runs are long and the sizing is driven by voltage drop rather than current — the same reason 8 AWG is a poor substitute there.
FAQ
What is 10 mm² in AWG? 7 AWG by cross-sectional area, at 10.6 mm². But 7 AWG is not commercially stocked and does not appear in the ampacity tables, so the practical choice is between 8 AWG and 6 AWG.
Can I use 8 AWG instead of 10 mm²? 8 AWG has 16% less copper and misses the 10 mm² resistance limit by 13%. On a short run with margin it may be acceptable. On a long run, where 10 mm² is usually specified for voltage drop, it is the wrong direction.
Is 10 mm² the same as 6 AWG? No. 6 AWG is 13.3 mm², a third larger. It is the safe substitute because it is the nearest stocked gauge that is not smaller than 10 mm².
Why is 7 AWG not available? Odd-numbered gauges are defined in the wire gauge standard but are not carried by distributors. Cable is supplied in even gauges and the 0-series. 7 AWG is also absent from the standard ampacity tables, so there is no published rating to design from.
What is 10 mm² in mm diameter? A solid conductor would be 3.568 mm across. Real 10 mm² cable is stranded and measures up to 4.2 mm, or 5.1 mm for flexible constructions.
How many amps is 10 mm² cable? 57 A for PVC clipped direct, 71 A for XLPE, with three loaded conductors at 30 °C ambient. Both figures fall sharply once you correct for the actual ambient temperature and the number of circuits sharing the route.
Reference
| Property | 10 mm² |
|---|---|
| Closest AWG by area | 7 AWG (10.6 mm², +6%) — not stocked |
| Commercial substitute | 6 AWG (13.3 mm², +33%) |
| Undersized option | 8 AWG (8.37 mm², −16%, fails the limit) |
| Equivalent solid diameter | 3.568 mm |
| Max resistance, class 1 and 2 | 1.83 Ω/km |
| Max resistance, class 5 and 6 | 1.91 Ω/km |
| Max conductor diameter | 3.7 / 4.2 / 5.1 mm by class |
| Ampacity, PVC clipped direct | 57 A before derating |
Work the other direction from 8 AWG or 6 AWG, or use the converter.