Wire Gauge Diameter Chart

Use this reference for nominal bare conductor diameter, then switch to manufacturer outside-diameter data when the task is physical installation fit.

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Quick reference table

Wire gauge diameter is a bare-metal geometry reference. It is useful for identification, drawing review, and AWG math, but it is not the diameter to use for conduit fill, tray fill, cable glands, or terminal fit. Physical installation work needs the finished insulated conductor or cable outside diameter from the product data.

Nominal bare AWG conductor diameters

Nominal bare AWG conductor diameters
AWG	Diameter inches	Diameter mm	Field use
18 AWG	0.0403	1.02	Small control conductors
16 AWG	0.0508	1.29	Control or fixture lead reference
14 AWG	0.0641	1.63	Small branch-circuit geometry
12 AWG	0.0808	2.05	Common branch-circuit geometry
10 AWG	0.1019	2.59	Equipment lead geometry
8 AWG	0.1285	3.26	Larger conductor cross-check

Which diameter belongs in the next task

Which diameter belongs in the next task
Task	Use this dimension	Do not use
Gauge identification	Bare conductor diameter or area	Insulation outside diameter alone
Conduit fill	Insulated conductor or cable outside diameter	Bare AWG diameter
Cable tray planning	Finished cable outside diameter or width	Conductor metal diameter
Terminal or lug fit	Manufacturer conductor range and class	A chart diameter without lug data

How to use this chart

Read it as bare conductor geometry

Use the chart to understand AWG bare diameter and gauge geometry before moving into installation-specific dimensions.

Switch dimensions for fit work

When the task is conduit fill, cable gland selection, tray spacing, or terminal fit, switch to the manufacturer outside-diameter or listed range.

Record construction details

Note whether the conductor is solid, stranded, compact, insulated, jacketed, or part of a multi-conductor cable assembly.

Formula basis

Diameter in inches = 0.005 x 92^((36 - AWG) / 39).

AWG is the gauge number.
Diameter is nominal bare conductor diameter before insulation or jacket construction.

Worked examples

10 AWG bare diameter versus building wire diameter

10 AWG bare conductor diameter is about 0.1019 in, but the installed wire outside diameter depends on insulation type and manufacturer construction.

Cable gland review

A cable gland needs the jacket outside diameter from the cable datasheet. The AWG bare conductor diameter is only a geometry reference.

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Frequently asked questions

These answers explain how to use the chart without turning a quick reference into a final design decision.

Can this chart be used for conduit fill?

No. Conduit fill depends on the outside diameter or area of insulated conductors or cables, not only the bare conductor diameter.

Why do two 12 AWG products have different finished diameters?

AWG describes conductor metal size. Insulation thickness, stranding, jacket, compact construction, and cable assembly design change finished diameter.

What should I use for lug fit?

Use the lug or terminal listing, conductor material, conductor class, and manufacturer range. A bare-diameter chart is not enough for termination approval.