16 gauge wire measures 1.29 mm across. That is 50.8 mils, or 0.0508 inches.
Almost everyone asking this question wants the diameter, not the cross-section. It is a ferrule question, a terminal question, or a “will this fit the connector” question. So the diameter comes first here — but the number you need is probably not 1.29 mm.
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Why 1.29 mm is usually the wrong number
1.29 mm is solid wire. 16 AWG in a panel, a fixture, or an appliance cord is almost always stranded, and stranding makes the bundle wider than the solid equivalent.
The metric size that covers 16 AWG is 1.5 mm². At that size the standard sets these maximum conductor diameters:
| Construction | Max diameter | Max strand dia. |
|---|---|---|
| Class 1, solid | 1.5 mm | — |
| Class 2, stranded | 1.7 mm | — |
| Class 5, flexible | 1.8 mm | 0.26 mm |
| Class 6, very flexible | 1.8 mm | 0.16 mm |
So the real range for a 16 AWG-equivalent conductor is 1.5 to 1.8 mm, not 1.29 mm. If you are picking a ferrule or checking a terminal clamp range, work from the upper figure and the cable manufacturer’s actual data.
Class 5 and class 6 look identical and behave differently
Note what the table above does not show: class 5 and class 6 share the same maximum diameter, 1.8 mm, and the same resistance limit, 13.3 Ω/km. On paper they are the same conductor.
The only difference in the standard is strand fineness — 0.26 mm for class 5, 0.16 mm for class 6.
That distinction decides whether the cable survives. Anything that flexes in service needs class 6: cabinet door looms, drag chains, robot dress packs, machine tool wiring. Class 5 in a repeatedly flexing application works fine for months, then work-hardens and a strand breaks, and you have an intermittent fault that takes a day to trace.
If the cable never moves after installation, class 2 or class 5 is fine and cheaper. The full breakdown is in conductor classes 1, 2, 5 and 6.
The cross-section, for when you need it
16 AWG is 1.31 mm². The metric size to order is 1.5 mm², which is 15% more copper.
A 16 AWG conductor runs about 13.19 Ω/km. The limit for 1.5 mm² is 12.1 Ω/km, so 16 AWG is roughly 9% too resistive to pass as 1.5 mm². It comfortably clears 1 mm² at 18.1 Ω/km.
That matters less here than at power sizes, because 16 AWG rarely carries current where a 9% resistance difference changes anything. It matters if a specification calls out 1.5 mm² conductor resistance and someone supplies 16 AWG against it.
Rounding down to 1 mm² costs 24% of the cross-section. At this size that is usually the wrong trade — the copper saving is negligible and the mechanical robustness drops.
Where 16 AWG is used
Fixture wire, luminaire tails, appliance cords, control panel interconnects, thermostat and low-voltage runs, and speaker cable. Inside a control panel it turns up where 18 AWG is not mechanically strong enough to survive handling but a full 14 AWG is unnecessary.
It is a light-duty conductor. The selection criteria are usually mechanical and dimensional — will it terminate, will it flex, will it survive being pulled — rather than ampacity.
FAQ
How many mm is 16 gauge wire? 1.29 mm in diameter for solid wire. Stranded 16 AWG runs wider, up to about 1.8 mm for flexible constructions.
What is 16 AWG in mm²? 1.31 mm². The metric cable size that replaces it is 1.5 mm².
Is 16 AWG the same as 1.5 mm²? No. 1.5 mm² has 15% more copper and a tighter resistance limit that 16 AWG does not meet. 1.5 mm² is the size you order to replace 16 AWG, not an equivalent you can substitute in reverse on a specification.
Can I use 1 mm² instead of 16 AWG? It is 24% less copper. Electrically that is usually acceptable at this size, but the conductor is noticeably less robust to handle and terminate. Consider it a downgrade.
What ferrule size do I need for 16 AWG? Ferrules are sized in mm², so you want a 1.5 mm² ferrule for most stranded 16 AWG. Check the conductor’s actual overall diameter against the ferrule barrel — strand count varies between manufacturers at the same nominal size.
Is 16 gauge thicker than 18 gauge? Yes. AWG runs backwards: a lower number is a thicker conductor. 16 AWG is 1.29 mm, 18 AWG is 1.02 mm. The reason is in how the AWG system works.
Reference
| Property | 16 AWG |
|---|---|
| Diameter, solid | 1.29 mm |
| Diameter, solid | 50.8 mils / 0.0508 in |
| Cross-sectional area | 1.31 mm² |
| Area | 2,580 cmil |
| Resistance, solid copper at 20 °C | 13.19 Ω/km |
| Metric size to order | 1.5 mm² (+15%) |
| Metric size below | 1 mm² (−24%) |
| Stranded conductor diameter | up to 1.8 mm |
Convert any other gauge with the AWG to mm² converter, or work the other direction from 1.5 mm² to AWG.