1 mm2 to AWG: 17 AWG, and Why You Cannot Buy It

1 mm² converts to **17 AWG**, at 1.04 mm². That is 4% larger than 1 mm² and it meets the resistance limit — a clean answer on paper.

The problem is that nobody sells 17 AWG.

Odd gauges exist and are not stocked

Odd-numbered gauges are defined in the wire gauge standard. They are not carried by distributors. Building wire, appliance wire and panel wire come in even gauges and the 0-series, so 17 AWG has an area, a diameter and a resistance, and no supply chain.

That leaves two real options:

16 AWG is the answer. It overshoots by nearly a third, which is more copper than the design called for, but it meets the requirement and it is available everywhere.

When 18 AWG is defensible

18 AWG misses the 1 mm² resistance limit by 16% — a wider miss than most, and not one you can argue away against a written specification.

But 1 mm² is a control and signal size, not a power size. Neither 1 mm² nor 18 AWG appears in the general ampacity tables, which start at 1.5 mm² on the metric side and stop at 18 AWG on the American side. Where these conductors carry current, the rating comes from the equipment standard or the flexible cord rules.

So the question is what the 1 mm² was specified for:

• A written specification or a conductor resistance test? 16 AWG. There is no argument to make.
• Matching an existing control circuit where the current is trivial? 18 AWG is 18% less copper on a conductor that is not thermally limited. Run the loop resistance for the actual length and record what you checked.
• A long signal run? 18 AWG at 20.95 Ω/km against 13.19 for 16 AWG is 59% more resistance per metre. On a 4-20 mA loop or a long RS-485 segment that goes into the circuit budget.

Conductor diameter

A solid conductor of 1 mm² works out to 1.128 mm across. The standard specifies maximums by class rather than a nominal value:

Solid 18 AWG measures 1.02 mm and solid 16 AWG measures 1.29 mm.

Class 5 and class 6 share the 1.5 mm maximum and the same resistance limit here. The only difference in the standard is strand fineness — 0.21 mm against 0.16 mm — and at this size that decides whether the conductor survives a cabinet door loom. See conductor classes 1, 2, 5 and 6.

Where 1 mm² is used

Control panel wiring, relay and contactor coils, instrumentation, lighting circuits in some installations, appliance internal wiring, and low-voltage signal runs.

It is the metric size that occupies roughly the same role as 18 AWG in North American practice, even though the two are not the same size — 18 AWG is 18% smaller.

FAQ

What is 1 mm² in AWG?

17 AWG by cross-sectional area, at 1.04 mm². Odd gauges are not stocked, so the practical choice is 18 AWG or 16 AWG.

Should I use 18 AWG or 16 AWG?

16 AWG if you are meeting a specification — 18 AWG misses the 1 mm² resistance limit by 16%. On a short control run where current is trivial, 18 AWG may be acceptable, but check the loop resistance for the actual length.

Is 1 mm² the same as 16 AWG?

No. 16 AWG is 1.31 mm², about 31% larger. It is the nearest stocked gauge that is not smaller than 1 mm².

Why can I not buy 17 AWG?

Odd-numbered gauges are defined in the wire gauge standard but distributors carry even gauges and the 0-series. See how the AWG system works.

What is 1 mm² in mm diameter?

A solid conductor is 1.128 mm across. Stranded measures up to 1.4 mm, flexible up to 1.5 mm.

How many amps does 1 mm² carry?

It is not listed in the general ampacity tables, which start at 1.5 mm². Where 1 mm² carries current, the rating comes from the equipment standard or the rules for flexible cords rather than the power circuit tables.

Reference

Work the other direction from 18 AWG or 16 AWG, or use the converter.