AWG to mm Calculator

Convert American Wire Gauge (AWG) to bare-conductor diameter (mm) or cross-section (mm²) using the ASTM B258 unrounded geometric progression (primary), with ASTM Table 1 SI standard nominals shown as a separate layer for integer gauges 4/0–56.

Default example: AWG 12 → 2.0525 mm · 3.3088 mm² (formula); Table 1 nominal 2.052 mm · 3.308 mm².

Supported and not supported

Supported

• Solid round AWG → diameter (field=mm) or round area (field=mm2); lookup always returns both
• Human tokens 12, 1/0, 4/0 (legacy −3…0 still accepted)
• Copper Ω/km at 20 °C as a material-model layer
• Educational NFPA 70–style thermal ampacity as a code-context-required reference when tabulated (source_family=NFPA_70, table_like=310.16, edition=null) — not a branch-circuit/OCPD rating
• Legacy query alias a for awg (chart / older links)
• API / SSR / local UI share engine awg · capability electrical.awg_to_mm

Not supported

• Stranded equivalent diameter or compact-stranded area tables
• Insulated / jacketed outer diameter
• Ampacity derating, OCPD sizing, or code-compliant cable design
• SWG / BWG (use the dedicated SWG tool)

Agent / API notes

Capability id: electrical.awg_to_mm · tool id: awg-to-mm · pin calculation_version: 1.5.0.

Result object layers: geometry (primary unrounded formula: formula_derived for integer 4/0–56, else formula_interpolation / formula_extrapolation; geometry.standard_nominal = ASTM B258 Table 1 when integer in-range; edition_kind=reapproval) · electrical (material_model @ 20 °C, ρ = 1.7241×10⁻⁸ Ω·m) · references.ampacity (code_context_required, educational, code_edition_not_pinned, jurisdiction_usable: false).

UI/share parameter: mode=awg-mm | awg-mm2. Engine/API parameter: field=mm | mm2 (mode is mapped to field on the page/SSR; API INVALID_MODE applies to field).

Stable error codes: MISSING_REQUIRED_INPUT, INVALID_NUMBER, INVALID_MODE. Warnings: AWG_NONSTANDARD_GAUGE (e.g. 12.5), AWG_OUTSIDE_STANDARD_RANGE (e.g. 100). geometry.range is standard_range | nonstandard_gauge | formula_extrapolation. Interpolated and extrapolated diameters are finite formula results, not ASTM Table 1 nominals.

What is AWG?

American Wire Gauge (AWG), also known as Brown & Sharpe, is the usual North American size system for solid round electrical conductors (copper, aluminum, and other non-ferrous metals). It defines diameter on a logarithmic scale so that each step is a constant ratio.

Key rules of thumb:

• The smaller the AWG number, the thicker the wire.
• The larger the AWG number, the thinner the wire.
• Example: AWG 4/0 (formula ≈11.684 mm; Table 1 nominal 11.68 mm) is far thicker than AWG 36 (0.127 mm).

Europe and much of the world specify cable by mm² cross-section instead. This calculator bridges the two: enter AWG, get diameter and area.

How to convert AWG to mm

Wire diameter

The gauge-n diameter dₙ in millimeters is:

dₙ (mm) = 0.127 mm × 92^((36−n)/39)

0.127 mm is the diameter of AWG 36. Across 39 gauge steps, diameter changes by a factor of 92.

Wire cross-section

For a round conductor:

Aₙ (mm²) = (π)/4 dₙ² = 0.012668 mm² × 92^((36−n)/19.5)

Heavy gauges (4/0 … 1/0)

Enter the label directly. Legacy numeric index still works.

AWG to mm conversion chart

Bare conductor values (no insulation). Diameter and area match the formulas above.

Inch diameters are dₘₘ / 25.4.

Choosing a metric cable from AWG

AWG almost never lands on a round mm² stock size. After converting:

1. Prefer the next larger standard metric cross-section when current or voltage drop matters.
2. For mains (e.g. 110 V / 230 V), very fine gauges are usually unsuitable — many installers treat about 0.5 mm² as a practical minimum for power conductors.
3. Signal, audio, and data lines may use thinner wires where voltage and current are low.
4. Confirm thermal ampacity, temperature rating, and local electrical code — diameter alone is not a current rating, and the 90 °C column is not a breaker size.

Approximate nearest common metric sizes (illustrative only):

Things to remember

• Gauge vs mm: smaller AWG → larger mm / mm².
• AWG ≠ SWG: British Standard Wire Gauge is a different table — use SWG to mm.
• Conductor only: published AWG sizes exclude insulation and sheath.
• Stranded vs solid: same AWG copper area, but stranded cable outer diameter depends on strand construction and may be larger than solid-conductor diameter. This calculator is not a stranded equivalent.
• Resistance & heating: thinner wire → higher resistance → more voltage drop and heat for a given current. Use the voltage drop calculator for long runs.