6 AWG in MM: Diameter, Cross-Sectional Area, and Metric Cable Equivalents

A drawing arrives marked "6 AWG copper." The supplier's quotation comes back in square millimetres. Between those two documents sits a conversion that is simple to perform and surprisingly easy to get wrong - and the penalty shows up later as an undersized feeder, a lug that will not crimp, or a load calculation that fails review.

The short answer: 6 AWG equals 4.115 mm in conductor diameter and 13.3 mm² in cross-sectional area. The diameter is an exact conversion from inches. The area is the geometric area of the metal, and it is not a standard metric cable size - which is why buyers in metric markets are almost always asked to choose between 10 mm² and 16 mm² as the substitute.

The sections below cover where those numbers come from, how they behave on stranded conductors, and how to pick a metric equivalent without giving away current-carrying capacity.

6 AWG in MM: The Numbers You Need

American Wire Gauge is an inch-based system, so every gauge has an exact metric equivalent. For 6 AWG the working values are a nominal diameter of 4.115 mm (0.1620 in), a cross-sectional area of 13.3 mm², and about 26,250 circular mils.

Two of those values are routinely confused. The 4.115 mm is the diameter of a solid round conductor, while 13.3 mm² is the area of the metal. When a specification says only "6 AWG," both numbers sit behind that designation, and it pays to know which one the other party actually needs.

How the Conversion Is Calculated

AWG diameters follow a geometric progression: d = 0.005 in × 92^((36 − n)/39), where n is the gauge number. For n = 6 the exponent is 30/39, the step factor works out to roughly 32.4, and the result is 0.1620 in. Multiply by 25.4 and you get 4.1148 mm, normally written as 4.115 mm.

Because the definition is anchored in inches and the inch is exactly 25.4 mm, the conversion itself introduces no approximation. When two online converters disagree - 4.115 mm against 4.1148 mm - that is a rounding choice, not a different answer. On a cable drawing, the gap is far below any practical tolerance.

Solid versus stranded measurement

On a solid 6 AWG conductor, a caliper across the copper should read close to 4.115 mm. On a seven-strand 6 AWG conductor, each strand is about 1.55 mm across and the bundle measures roughly 4.6 to 4.7 mm, even though the metal area is identical. This is the most common reason a technician believes a shipment is out of specification when it is perfectly normal.

What "nominal" means on a datasheet

AWG dimensions are published as nominal values. Standards set the nominal diameter for each gauge and, separately, the tolerances that apply to finished cable, insulation thickness, and electrical performance. If you need an inspection criterion, work from the applicable conductor standard rather than comparing a caliper reading against 4.115 mm. For any electrical calculation, the number that matters is the area - 13.3 mm² - because resistance, ampacity, and voltage drop all follow from it.

Matching 6 AWG to the Nearest Metric Cable Size

Metric cable is manufactured in fixed steps: 1.5, 2.5, 4, 6, 10, 16, 25 mm², and so on. Since 13.3 mm² is not one of them, a 6 AWG conductor is normally replaced by 10 mm² (close to 8 AWG) or by 16 mm² (close to 5 AWG). Both substitutions can be right, but not for the same reason.

• Choose 16 mm² when the original 6 AWG was sized for current-carrying capacity or for voltage drop over a long run. It is larger in area than 6 AWG, so ampacity is preserved with margin.
• Choose 10 mm² only when the original size was driven by mechanical strength, conduit fill, or terminal dimensions, and the connected load stays comfortably inside the smaller conductor's rating.

For orientation, IEC-style installation tables commonly place a 10 mm² PVC-insulated copper conductor in the low 50 A range under typical fixing methods, while 16 mm² reaches roughly 70 A. The exact figure depends on insulation material, the number of loaded conductors, ambient temperature, and installation method. Our LV power cables cover this size range, which makes side-by-side substitution straightforward when a design moves between AWG and metric sizing.

Ampacity and Resistance: The Numbers That Size a Cable

A diameter conversion tells you whether a lug will fit. It does not tell you whether the circuit will work. That answer comes from ampacity and resistance, and 6 AWG has well-established values for both.

On resistance, 6 AWG copper measures about 1.61 Ω per km at 20 °C (0.491 Ω per 1,000 ft), and 6 AWG aluminum about 2.65 Ω per km. Resistance climbs with temperature - roughly 20% higher at 75 °C than at 20 °C for copper - so voltage-drop work done with room-temperature figures is slightly optimistic.

As a worked example, a 50 m run of 6 AWG copper carrying 60 A on a 240 V single-phase circuit loses about 9.7 V over the round trip, close to 4% of supply voltage, and a little more once the conductor reaches operating temperature. Push the same load to 80 m and stepping up to a 16 mm² conductor turns from a technicality into an economic decision. Our published LV power cable selection guide follows the same sizing logic with worked examples.

Where 6 AWG Appears in Real Projects

The gauge turns up in a fairly consistent set of applications:

• Sub-panel feeders and service conductors in residential and light commercial work, typically on 50 A to 60 A circuits.
• Level 2 electric vehicle charger circuits, where a continuous load requires a correspondingly rated branch circuit.
• Battery, inverter, and DC bus connections in off-grid, backup power, RV, and marine systems.
• Solar combiner-to-inverter runs, where current from several strings is aggregated before the inverter.
• Equipment grounding conductors and bonding jumpers in larger distribution panels.

When these projects are built to metric documentation, the substitution above is routine. For 450/750 V building wiring, a PVC-insulated conductor in 10 or 16 mm² lands in the same terminals as 6 AWG in most panel work:

PVC-Insulated 450/750 V Building Wire for Fixed WiringCost-effective PVC-insulated copper cable for 450/750 V fixed power and lighting wiring, suitable for metric building-wiring substitutions in panel work.View Product →

On the DC side of a solar array, the conductor also has to survive UV exposure, ozone, and wide temperature swings, which is a different requirement from ampacity alone:

Photovoltaic DC Cables for Solar Module and Combiner ConnectionsSingle-core flexible PV cables with tinned copper and XLPO insulation for outdoor solar DC connections subject to UV, ozone, and temperature swings.View Product →

Specifying and Ordering the Metric Equivalent

The conversion is the easy part. The ordering paperwork is where the expensive mistakes happen, so a few points belong on your checklist.

1. Confirm which system the number belongs to. A "6" on a European datasheet means 6 mm², not 6 AWG. That is roughly 9.5 AWG and about 45% of the copper area of a 6 AWG conductor - a gap wide enough to fail a load calculation. Never treat the digits as interchangeable.
2. State the conductor class. AWG conductors are commonly supplied as 7-strand or 19-strand, while IEC 60228 uses Class 2 for stranded and Class 5 or 6 for flexible. A flexible 16 mm² and a rigid 16 mm² share the same area but behave completely differently in bend radius and terminations.
3. Name the standard. UL 44, UL 83, IEC 60502-1, and BS 6004 each define their own insulation thicknesses, test voltages, and temperature ratings, so a 16 mm² conductor built to one standard is not automatically a drop-in replacement for a 6 AWG conductor built to another.
4. Check the temperature rating before comparing ampacity tables. A conductor rated 90 °C carries more current than the same area rated 70 °C, and the comparison only holds when both are evaluated under the same conditions.
5. Match the terminal as well as the current. Conductor area determines current capacity; stranding and overall diameter determine whether the lug crimps correctly.

Where a metric equivalent will sit permanently in feeder and distribution work, XLPE insulation provides more thermal headroom at the same cross-section:

CU/XLPE/PVC 0.6/1 kV Single-Core Unarmored Power CableXLPE-insulated copper cable for fixed feeder and distribution work, worth checking when a metric equivalent must carry the required ampacity.View Product →

6 AWG is 4.115 mm across and 13.3 mm² in area, and those two facts solve different problems: one fits the lug, the other carries the current. When a drawing has to be built in metric cable, 16 mm² is the safe substitution for ampacity, while 10 mm² works only where the load allows it. Confirm the standard, the stranding class, and the temperature rating before the order leaves the desk, and the conversion stops being a source of risk.