What is 12 AWG in mm²?

12 AWG = 3.31 mm² exactly (cross-section). The closest IEC 60228 standard size is 4 mm² — round up. Ampacity comparison: 12 AWG copper at 75 °C is rated 25 A per NEC 310.16; 4 mm² copper at 70 °C is rated about 27 A in BS 7671 reference Method C. Use 12 AWG / 4 mm² for typical 20 A residential branch circuits in North America (NEC required minimum on receptacle circuits).

What is 10 AWG to mm²?

10 AWG = 5.26 mm² exactly. Round to 6 mm² per IEC 60228. Ampacity: 10 AWG copper THWN-2 at 75 °C → 35 A; 6 mm² copper at 70 °C in BS 7671 → about 36 A in conduit. Used for 30 A branch circuits (clothes dryers, water heaters, small AC condensers).

What is 16 AWG in mm²?

16 AWG = 1.31 mm². Round to 1.5 mm² per IEC 60228. Ampacity is fixture-wire scale: 16 AWG copper rated about 18 A at 90 °C (NEC 402.5 chassis-wire); 1.5 mm² copper rated about 16 A at 70 °C (BS 7671). Both used for lighting branch circuits in their respective markets.

What is 16 mm² to AWG?

16 mm² = 6 AWG (closest standard). Exact: 16 mm² = 31.6 kcmil ≈ 5.7 AWG. Round to the next larger AWG (smaller number) for safety: 6 AWG copper at 75 °C → 65 A per NEC 310.16; 16 mm² copper at 70 °C → about 65–80 A depending on installation method per BS 7671 Table 4D1A. Match by ampacity, not by direct cross-section.

What is 25 mm² to AWG?

25 mm² ≈ 4 AWG (4 AWG = 21.2 mm²). Round up to 3 AWG (26.7 mm²) for slightly more capacity. NEC 4 AWG @ 75 °C → 85 A; BS 7671 25 mm² → about 100 A in free air, 85 A in conduit Method C — comparable.

What is 35 mm² to AWG?

35 mm² ≈ 2 AWG (2 AWG = 33.6 mm²). For the next larger: 1 AWG = 42.4 mm². NEC 2 AWG @ 75 °C → 115 A; BS 7671 35 mm² → about 120 A free-air, 100 A in conduit.

What is 50 mm² to AWG?

50 mm² ≈ 1/0 AWG (1/0 = 53.5 mm²). NEC 1/0 @ 75 °C → 150 A; BS 7671 50 mm² copper → about 150 A free-air, 130 A in conduit.

How do I convert mm to AWG (diameter, not area)?

For solid wire diameter: AWG ≈ −39 × log₁₀(d_mm / 0.127) / log₁₀(92) + 36. Quick reference: 4 mm Ø ≈ 6 AWG; 2.5 mm Ø ≈ 10 AWG; 1.6 mm Ø ≈ 14 AWG; 1.0 mm Ø ≈ 18 AWG. For stranded cable specified by diameter, use the manufacturer's data sheet — stranded conductor diameter is larger than the equivalent solid (typical fill 78–80 %).

Reference · Electrical · AWG ↔ mm² · IEC 60228 · NEC 310.16 · ASTM B258

AWG ↔ mm² — Wire Size Conversion Chart & Calculator

A complete AWG ↔ mm² conversion reference for cross-border electrical work — covering every gauge from 4/0 (≈ 107 mm²) down to 40 AWG, plus the common metric-to-imperial questions like 16 mm² → 6 AWG, 25 mm² → 4 AWG, 35 mm² → 2 AWG, and 50 mm² → 1/0 AWG. Includes the exact Brown & Sharpe formula, the standard IEC 60228 round-up logic, and ampacity columns from NEC 310.16 and BS 7671 / IEC 60364 side-by-side. Reviewed by a licensed PE.

Wire size calculator with AWG ↔ mm²

The embedded calculator works in either system: enter your load and choose AWG (NEC 310.16) or mm² (IEC 60228). It returns the smallest matching conductor with ampacity, voltage drop, and conduit fill. Useful as a mm2 value checker when verifying a metric specification meets the local NEC requirement, or vice versa. The output displays both AWG and the closest IEC 60228 standard mm² size.

CALC.003 Wire Size · NEC 310.16 · 6 presets · ampacity + VD

Application[App]

NEC 210.19(A) recommends ≤3% VD on branch, ≤5% combined feeder + branch.

Material[Mat]

Size standard[Std]

Insulation rating[°C]

Ambient temp[Ta]

°C

Load current[I]

or power[P]

System voltage[V]

Power factor[cos φ]

cos φ

Length one-way[L]

VD limit[%]

Conductors in raceway[N]

Parallel sets[Par]

Continuous load (3+ hrs at full current → ×1.25 NEC 210.19)

Recommended size

12 AWG

Both ampacity and voltage drop pass with margin.

0%3%6%

Voltage drop: — V (—%)
Ampacity (derated): —
Required ampacity: —
Recommended OCPD: —
Min EGC (NEC 250.122): —
Power loss in run: — W
V at load: — V

PASS · NEC 310.16 + 210.19(A)

A_min = max( A_vd , A_ampacity ) · NEC 310.16 NEC 240.4(D) · 250.122 · 310.15(B)

Conversion formulas

Eq. 01 — Exact AWG → mm² (Brown & Sharpe + cmil + 25.4 mm/in) SI

A_{mm^2} = \frac{\pi}{4} \cdot \left( 0.005 \cdot 92^{(36 - n)/39} \cdot 25.4 \right)^2

·: n = AWG number. For 4/0 use n = -3, 3/0 use -2, 2/0 use -1, 1/0 use 0.
·: Inner term is the diameter in mm; squaring + π/4 gives circular area in mm².
·: Result agrees with NEC and ASTM B258 tables to four significant figures.

Eq. 02 — mm² → AWG (inverse, useful for IEC ↔ NEC mapping) SI

n = 36 - 39 \cdot \log_{92}\!\left( \frac{1}{0.005 \cdot 25.4} \sqrt{\frac{4 A_{mm^2}}{\pi}} \right)

·: Round n DOWN (smaller AWG number = larger conductor) for engineering safety.
·: 4 mm² → n ≈ 11.0 → use 11 AWG (or commonly 10 AWG, the next smaller standard).
·: 16 mm² → n ≈ 5.7 → use 6 AWG (round to next standard available).

Eq. 03 — Quick rule: every 3 AWG steps doubles area SI

A_{n-3} = 2 \cdot A_n; \quad A_{n-6} = 4 \cdot A_n

·: Useful for mental arithmetic: 14 AWG = 2.08 mm² → 11 AWG ≈ 4.16 → 8 AWG ≈ 8.37 mm².
·: Diameter doubles every 6 AWG steps (14 AWG = 1.63 mm Ø → 8 AWG = 3.26 mm Ø).
·: Foundation of why the AWG ladder works as a logarithmic series in 92^(1/39).

Standards governing the conversion

Standard	Scope	Region
ASTM B258-18	Standard nominal diameters of solid round AWG copper wire	USA
NEC / NFPA 70 — Table 310.16	Allowable ampacity by AWG and insulation temperature	USA
IEC 60228:2004	Conductor cross-sectional areas (mm²) — the metric standard	Worldwide
BS 7671 — UK Wiring Regs	Tables 4D1A–4F3A: ampacity for IEC 60228 sizes by installation method	UK
IEC 60364	Low-voltage installations — methods of installation and grouping factors	Worldwide
AS/NZS 3008	Cable selection for low voltage — AS/NZS uses IEC 60228 sizes	Australia / NZ

AWG ↔ mm² chart with ampacity

Full ampacity chart awg with the closest IEC 60228 size and both NEC + BS 7671 ratings. The "mm to AWG chart" / "mm2 drawing" reference for cable design.

AWG	Diameter (mm)	Area (mm²)	Closest IEC 60228 (mm²)	NEC 75 °C Cu (A)	BS 7671 ref (Method C, A)
4/0	11.68	107.2	120	230	~ 285
3/0	10.40	85.0	95	200	~ 245
2/0	9.27	67.4	70	175	~ 200
1/0	8.25	53.5	50	150	~ 145
1	7.35	42.4	35–50	130	~ 120
2	6.54	33.6	35	115	~ 110
4	5.19	21.2	25	85	~ 90
6	4.11	13.3	16	65	~ 70
8	3.26	8.37	10	50	~ 50
10	2.59	5.26	6	35	~ 36
12	2.05	3.31	4	25	~ 27
14	1.63	2.08	2.5	20	~ 22
16	1.29	1.31	1.5	— *	~ 16
18	1.02	0.823	1.0	— *	~ 13
20	0.812	0.518	0.5	— *	~ 9
22	0.644	0.326	0.34	— *	~ 5

* AWG 16 and smaller are not in NEC Table 310.16 (general power wiring starts at 14 AWG). Values shown are typical fixture-wire / chassis-wire ampacities (NEC 402.5).

Find the AWG number on the cable jacket or specification. NEC building wire is printed every 24" with the AWG (e.g., "12 AWG THWN-2 600V"). For metric cables specified in mm², find the manufacturer's spec sheet. The two numbering systems are inverse: smaller AWG number = bigger conductor; larger mm² value = bigger conductor.
Apply the AWG → mm² formula or use the lookup table. Exact conversion: A_mm² = (π / 4) × (0.005 × 92^((36 − n)/39) × 25.4)² where n is the AWG number. Practical: 14 AWG ≈ 2.08 mm², 12 AWG ≈ 3.31 mm², 10 AWG ≈ 5.26 mm², 8 AWG ≈ 8.37 mm², 6 AWG ≈ 13.30 mm², 4 AWG ≈ 21.15 mm². For 4/0 (-3 in formula): 107.2 mm².
Round to the nearest IEC 60228 standard size. AWG sizes do not map cleanly to IEC values. Round UP for safety: 12 AWG (3.31 mm²) → IEC 4 mm². 10 AWG (5.26 mm²) → IEC 6 mm². 8 AWG (8.37 mm²) → IEC 10 mm². 6 AWG (13.3 mm²) → IEC 16 mm². Standard IEC 60228 sizes: 0.5, 0.75, 1, 1.5, 2.5, 4, 6, 10, 16, 25, 35, 50, 70, 95, 120, 150, 185, 240, 300, 400, 500, 630, 800, 1000 mm².
Verify ampacity in the local code, not by cross-conversion. NEC 310.16 (75 °C Cu) and IEC 60364 (BS 7671 Tables 4D1A through 4F3A) use different installation methods, ambient assumptions, and grouping factors. Always size from the code in force at the installation site — never just convert the cross-section and assume identical ampacity.

Worked example — German equipment on a US 480 V feeder

A European-built CNC machine arrives in a Texas plant with a nameplate calling for "3 × 16 mm² + 16 mm² PE" feeder on its 480 V 3-phase service. Walk through the conversion to NEC sizing:

Step 1 — direct conversion: 16 mm² ≈ 6 AWG (6 AWG = 13.3 mm² is slightly smaller; 4 AWG = 21.2 mm² is slightly larger). For exact equivalence, use 4 AWG (next larger). For NEC compliance, the rule is "not less than the European spec" → 6 AWG copper meets cross-section but check ampacity.

Step 2 — ampacity check: 6 AWG copper THWN-2 @ 75 °C = 65 A per NEC 310.16. The European 16 mm² @ 70 °C in conduit per BS 7671 Method C = ~ 65 A. Match.

Step 3 — load verification: machine nameplate FLA = 50 A. 6 AWG copper (65 A) provides 30 % margin (NEC 215.3 needs ≥ 25 % for continuous). OK.

Step 4 — final spec: order 3 × 6 AWG THWN-2 + 1 × 10 AWG green ground in 1¼" EMT (NEC 250.122 ground sized for 60 A breaker). Document on the panel schedule as "feeder upsized from European 16 mm² spec to NEC 6 AWG copper THWN-2".

AWG vs mm² — when each system wins

Aspect	AWG (North America)	mm² (IEC / Europe)
Numbering direction	Smaller number = bigger wire (counter-intuitive)	Bigger number = bigger wire (intuitive)
Step ratio	Geometric (92^(1/39) ≈ 1.123 per step)	Approximately decimal (1, 1.5, 2.5, 4, 6, 10, 16…)
Ampacity table	NEC 310.16 (60 / 75 / 90 °C, dry/wet)	BS 7671 / IEC 60364 (Methods A through G, ambient 30 °C)
Conduit fill	NEC Chapter 9 Tables 4 / 5 (in²)	IEC 61386 / BS 7671 (mm²)
Common everyday sizes	14 / 12 / 10 / 8 / 6 AWG	1.5 / 2.5 / 4 / 6 / 10 / 16 mm²
Used in	USA, Canada, parts of Latin America	EU, UK, Australia, NZ, India, Japan, China, Africa

Variants and special conversion cases

AWG sizes — diameter, area, ampacity

AWG (American Wire Gauge) is the North American conductor sizing system standardised by ASTM B258. The most commonly searched gauges: 2 AWG carries 95 A at 60 °C, 115 A at 75 °C, and 130 A at 90 °C (copper, NEC 310.16). 18 AWG is not in the general-power table — typical fixture-wire ampacity is 14 A at 90 °C (NEC 402.5). 6 AWG is 4.11 mm in diameter and 13.3 mm² in area, 8 AWG is 8.37 mm² (round up to 10 mm² for IEC equivalence). For metric-to-AWG: 4 mm² ≈ 11 AWG (use 10 AWG), and 2.5 mm² rounds to 14 AWG.

mm² sizes — IEC 60228 standard ladder

mm² (square millimetre) is the metric conductor cross-section per IEC 60228. The standard ladder runs 0.5, 0.75, 1, 1.5, 2.5, 4, 6, 10, 16, 25, 35, 50, 70, 95, 120, 150, 185, 240, 300, 400, 500, 630, 800, and 1000 mm². The most common cross-conversions: 10 mm² ≈ 8 AWG, 16 mm² ≈ 6 AWG, 25 mm² ≈ 4 AWG. To get diameter from area, take √(area × 4 / π) — so 16 mm² is 4.51 mm in diameter. The embedded calculator above does exact bidirectional conversion. IEC additionally defines stranded conductor classes (1 solid, 2 stranded, 5 flexible, 6 extra-flexible) — same nominal mm² but different physical diameters.

Frequently asked questions

What is 12 AWG in mm²?: 12 AWG = 3.31 mm² exactly (cross-section). The closest IEC 60228 standard size is 4 mm² — round up. Ampacity comparison: 12 AWG copper at 75 °C is rated 25 A per NEC 310.16; 4 mm² copper at 70 °C is rated about 27 A in BS 7671 reference Method C. Use 12 AWG / 4 mm² for typical 20 A residential branch circuits in North America (NEC required minimum on receptacle circuits).
What is 10 AWG to mm²?: 10 AWG = 5.26 mm² exactly. Round to 6 mm² per IEC 60228. Ampacity: 10 AWG copper THWN-2 at 75 °C → 35 A; 6 mm² copper at 70 °C in BS 7671 → about 36 A in conduit. Used for 30 A branch circuits (clothes dryers, water heaters, small AC condensers).
What is 16 AWG in mm²?: 16 AWG = 1.31 mm². Round to 1.5 mm² per IEC 60228. Ampacity is fixture-wire scale: 16 AWG copper rated about 18 A at 90 °C (NEC 402.5 chassis-wire); 1.5 mm² copper rated about 16 A at 70 °C (BS 7671). Both used for lighting branch circuits in their respective markets.
What is 16 mm² to AWG?: 16 mm² = 6 AWG (closest standard). Exact: 16 mm² = 31.6 kcmil ≈ 5.7 AWG. Round to the next larger AWG (smaller number) for safety: 6 AWG copper at 75 °C → 65 A per NEC 310.16; 16 mm² copper at 70 °C → about 65–80 A depending on installation method per BS 7671 Table 4D1A. Match by ampacity, not by direct cross-section.
What is 25 mm² to AWG?: 25 mm² ≈ 4 AWG (4 AWG = 21.2 mm²). Round up to 3 AWG (26.7 mm²) for slightly more capacity. NEC 4 AWG @ 75 °C → 85 A; BS 7671 25 mm² → about 100 A in free air, 85 A in conduit Method C — comparable.
What is 35 mm² to AWG?: 35 mm² ≈ 2 AWG (2 AWG = 33.6 mm²). For the next larger: 1 AWG = 42.4 mm². NEC 2 AWG @ 75 °C → 115 A; BS 7671 35 mm² → about 120 A free-air, 100 A in conduit.
What is 50 mm² to AWG?: 50 mm² ≈ 1/0 AWG (1/0 = 53.5 mm²). NEC 1/0 @ 75 °C → 150 A; BS 7671 50 mm² copper → about 150 A free-air, 130 A in conduit.
How do I convert mm to AWG (diameter, not area)?: For solid wire diameter: AWG ≈ −39 × log₁₀(d_mm / 0.127) / log₁₀(92) + 36. Quick reference: 4 mm Ø ≈ 6 AWG; 2.5 mm Ø ≈ 10 AWG; 1.6 mm Ø ≈ 14 AWG; 1.0 mm Ø ≈ 18 AWG. For stranded cable specified by diameter, use the manufacturer's data sheet — stranded conductor diameter is larger than the equivalent solid (typical fill 78–80 %).

The Brown & Sharpe geometric series

The American Wire Gauge series is a geometric progression in which each successive gauge step changes the wire diameter by the ratio (92)^(1/39). The endpoints 4/0 (= 0.4600 in) and 36 (= 0.005 in) are exact by definition; every other size is computed from the formula d_n = 0.005 × 92^((36 − n)/39). To convert to the metric mm² scale use d_mm = 25.4 × d_in and A_mm² = (π/4) × d_mm². The mapping is irrational by construction — there is no AWG number whose mm² area exactly matches a standard IEC 60228 size.

ASTM B258-18 — Standard Specification for Standard Nominal Diameters and Cross-Sectional Areas of AWG Sizes of Solid Round Wires Used as Electrical Conductors → § 4.1 — Diameter formula

Related calculators and references

Sources and further reading

ASTM International. ASTM B258-18 — Standard Specification for Standard Nominal Diameters and Cross-Sectional Areas of AWG Sizes of Solid Round Wires Used as Electrical Conductors.
IEC. IEC 60228:2004 — Conductors of insulated cables. The IEC standard for metric mm² conductor sizes 0.5–2 500 mm².
NFPA. NFPA 70 — National Electrical Code (2023), Article 310 — conductor types, ampacity, ratings.
IET. BS 7671 — Requirements for Electrical Installations (UK Wiring Regulations), 18th Edition + Amendment 2:2022. Tables 4D1A–4F3A for cable current-carrying capacity.
Standards Australia. AS/NZS 3008.1.1:2017 — Electrical installations: Selection of cables. The ANZ application of IEC 60228.
Mike Holt Enterprises. Understanding the National Electrical Code, Vol. 1. Industry reference for NEC sizing logic with AWG worked examples.