The AWG to mm² SWG Converter translates between American Wire Gauge, metric cross-section (mm²), and Standard Wire Gauge. Critical for electrical engineers and designers working across US, European, and British wiring standards where incompatible gauge systems cause costly specification errors.
2.0525
mm
3.3089
mm²
0.08081
in
6.53
kcmil
14
SWG
5.211
Ω/km
8.542
Ω/km
2.0525
mm
3.3089
mm²
0.08081
in
6.53
kcmil
14
SWG
5.211
Ω/km
8.542
Ω/km
A US electrical engineer specifies 10 AWG wire. A European supplier quotes 6 mm². A British contractor uses SWG. These three numbers refer to approximately the same conductor cross-section — but "approximately" is not good enough when you are sizing a cable for a 30-ampere circuit or specifying transformer windings. The calculator for AWG/mm²/SWG conversion provides precise, bidirectional translation between all three gauge systems, eliminating the specification ambiguity that causes both safety hazards and procurement errors.
All three systems have different mathematical bases that make direct comparison non-trivial:
Use this online calculator to convert any gauge value across all three systems. The ampacity calculator uses wire cross-section to determine current-carrying capacity.
The exact conversion formula: diameter (mm) = 0.127 × 92^((36−AWG)/39); area (mm²) = π/4 × diameter². Practical reference table for the most common conductor sizes:
Note that IEC standard sizes are the next larger standard size above the AWG exact area — European cables are typically slightly oversized relative to their AWG equivalents, providing a small safety margin.
The ampacity of a wire depends on cross-sectional area, conductor material (copper vs. aluminum), insulation type, installation method, and ambient temperature. Cross-system comparison requires care because AWG and IEC rating tables assume different installation conditions:
The conductor resistance calculator and conductor property calculators provide complementary electrical cable analysis tools.
Wire gauge specification errors have caused real engineering failures. A common scenario in international projects: a US-designed motor control panel specifies 12 AWG (3.31 mm²) control wiring; the overseas fabricator interprets this as 12 mm² (equivalent to approximately 4 AWG) — the panel arrives with massively oversized wiring that won't fit the intended terminals. The reverse is worse: specifying 1.5 mm² IEC but receiving 1.5 AWG (a cable nearly 14 mm in diameter used in industrial feeder circuits) — an error that would cause immediate equipment damage. Always specify both the gauge system and the metric cross-section area on international procurement documents to eliminate ambiguity.
The AWG diameter formula d = 0.127 × 92^((36−n)/39) mm is applied directly, where n is the AWG size (with 1/0 = 0, 2/0 = −1, 3/0 = −2, 4/0 = −3). Cross-sectional area is π(d/2)². The SWG approximation uses an inverse logarithmic mapping of the diameter onto the SWG scale. DC resistance = resistivity / area, using 17.241 nΩ·m for copper and 28.264 nΩ·m for aluminum. Ampacity is estimated from an empirical formula scaled by area^0.5, material factor, insulation temperature rating, and a temperature correction factor per NEC Table 310 methodology.
Diameter and Area: Use these for precise calculations — nominal mm² sizes round to standard values, but calculated area is exact. SWG Approx: Round to nearest integer for practical use. DC Resistance: Use for voltage drop calculations (multiply by circuit length in km). Ampacity: This is an approximation for in-conduit installation — always verify against NEC Table 310 or IEC 60364-5-52 for final design. Derate for multiple conductors in conduit, elevated ambient temperature, or direct burial.
Inputs
Results
AWG 12 copper — the most common residential branch circuit wire in North America — has a 2.05 mm diameter and 3.31 mm² cross-section, approximately SWG 14. Its 75°C ampacity is 20 A, matching the NEC standard 20 A branch circuit rating. The nearest IEC metric size is 2.5 mm² (standard European equivalent for 16–20 A circuits).
Inputs
Results
2/0 AWG aluminum (n = −1) gives a 10.4 mm diameter conductor with 85 mm² area — nearest metric size is 95 mm². At 90°C insulation in 40°C ambient, the ampacity is approximately 112 A. This is typical for 100 A service entrance feeders using aluminum to save cost on long runs.
The AWG system originated from the number of drawing dies a wire was pulled through to reach its final diameter. More pulls (higher AWG number) = thinner wire. The system was standardized in the 1850s and, despite its counterintuitive numbering, remains the standard in North America. The metric mm² system is more intuitive — larger numbers always mean larger conductors.
AWG 12 has a cross-sectional area of about 3.31 mm². The nearest standard metric size is 2.5 mm² (slightly smaller, rated 16–20 A) or 4 mm² (slightly larger, rated 25–32 A). In European practice, 2.5 mm² is the standard equivalent for 20 A circuits, corresponding to AWG 12 for most practical purposes. When specifying internationally, always state both the AWG and mm² sizes to avoid ambiguity.
No — 'gauge' is a generic term and the numbers differ between systems. AWG 14 ≠ SWG 14. AWG 14 has a diameter of 1.628 mm; SWG 14 has a diameter of 2.032 mm — a significant difference. Always specify which gauge standard you are using. In electronics, 'gauge' without qualification usually means AWG in North American contexts and SWG in British/Commonwealth contexts.
Ampacity (current-carrying capacity) depends on: conductor size and material; insulation temperature rating (60°C, 75°C, 90°C); installation method (open air, conduit, cable tray, buried); number of conductors bundled together; and ambient temperature. NEC Table 310.16 provides the definitive ampacity values for standard installations. Key values: AWG 14 Cu 15 A, AWG 12 Cu 20 A, AWG 10 Cu 30 A, AWG 8 Cu 50 A, AWG 6 Cu 65 A (all at 75°C, in conduit).
Aluminum has about 61% the conductivity of copper but only 30% the density and roughly 50% the cost per unit weight. For large conductors (above AWG 2 or 35 mm²), aluminum provides significant cost and weight savings. To carry the same current, aluminum wire needs to be approximately 1.5–2 AWG sizes larger than copper. Aluminum is commonly used for service entrance cables, feeder conductors, overhead distribution lines, and bus bars. Special terminations are required to prevent galvanic corrosion at connections.
The Standard Wire Gauge (SWG or British Standard Wire Gauge, BSWG) is defined by BS 3737:1964. It is used in the UK, Ireland, India, Australia (alongside metric), and other Commonwealth countries, particularly for: transformer and motor windings (enameled copper wire), telecommunications cables, fuse wire, and hobbyist electronics. While metric dimensions are increasingly preferred in professional engineering, SWG remains common in the electronics hobbyist community and in countries with strong British manufacturing heritage.
The IEC standard metric sizes are: AWG 18 ≈ 0.75 mm²; AWG 16 ≈ 1.5 mm²; AWG 14 ≈ 2.5 mm²; AWG 12 ≈ 4 mm²; AWG 10 ≈ 6 mm²; AWG 8 ≈ 10 mm²; AWG 6 ≈ 16 mm²; AWG 4 ≈ 25 mm²; AWG 2 ≈ 35 mm²; AWG 1/0 ≈ 50 mm²; AWG 2/0 ≈ 70 mm²; AWG 3/0 ≈ 95 mm²; AWG 4/0 ≈ 120 mm². These are approximate nearest standard sizes — always verify the exact area and verify ampacity for the specific installation.
AWG size refers to the total equivalent solid conductor cross-section, regardless of stranding. A 7-strand AWG 12 wire has the same total copper area as a solid AWG 12 wire. However, the overall diameter is slightly larger due to the gaps between strands. Stranded wire is more flexible and fatigue-resistant. The fill factor for stranded conductors is approximately 0.9–0.95 (the actual copper area is slightly less than the circle defined by the outer diameter). AWG and mm² designations always refer to the nominal conductor area, not the overall cable diameter.
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