Wire Size Conversion Calculator
AWG to diameter and area
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Quick Answer
AWG (American Wire Gauge) is a logarithmic scale where lower numbers = thicker wire. The formula d(mm) = 0.127 × 92^((36-AWG)/39) converts any gauge to diameter. Each 3 AWG steps doubles the cross-sectional area and halves the resistance.
Wire Size Calculator
Convert between AWG and metric mm2 and determine current-carrying capacity for copper conductors.
AWG to mm2
- AWG 10 = 5.26 mm2
- AWG 12 = 3.31 mm2
- AWG 14 = 2.08 mm2
- AWG 16 = 1.31 mm2
- AWG 18 = 0.82 mm2
- AWG 20 = 0.52 mm2
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Design Notes
AWG is used throughout North America while IEC metric sizes (mm²) are standard in Europe and Asia. There is no exact 1:1 mapping between the systems. For current-carrying capacity, always consult your local electrical code (NEC in the US, IEC 60364 internationally) as ampacity depends on installation conditions.
Common Mistakes
- 1
Thinking higher AWG = thicker wire. It is the OPPOSITE: AWG 10 is much thicker than AWG 24.
- 2
Using the same ampacity rating for wire in conduit vs free air — bundled wires must be derated significantly.
- 3
Ignoring voltage drop for long wire runs — even if the wire can handle the current, the voltage drop may be excessive.
Engineering Handbox
1. d(inches) = 0.005 × 92^((36-12)/39) = 0.0808 in 2. d(mm) = 0.127 × 92^0.615 = 2.053 mm 3. Area = π/4 × 2.053² = 3.31 mm² 4. Ampacity (NEC): 20A in 60°C insulation
Knowledge Base
Does higher AWG mean thicker wire?
No, AWG is inverted — a lower number means thicker wire. AWG 10 (2.59mm diameter) is much thicker than AWG 24 (0.51mm). The scale starts at 0000 (4/0), the thickest standard size at 11.68mm, and goes up to AWG 40 (0.08mm). Think of AWG as the number of times the wire was drawn through progressively smaller dies.
What is the AWG to mm conversion formula?
d(mm) = 0.127 × 92^((36 - AWG) / 39). This logarithmic formula means each 3 AWG steps approximately doubles the cross-sectional area (and halves the resistance). Each 6 AWG steps doubles the diameter. There is no simple linear conversion between AWG and metric sizes.
What AWG wire do I need for a 15A circuit?
For residential 15A circuits: AWG 14 minimum (NEC requirement in the US). For 20A circuits: AWG 12. For 30A: AWG 10. For 40A: AWG 8. For 50A: AWG 6. Always follow your local electrical code — these are minimums. Longer runs require upsizing to limit voltage drop.
What is the current capacity (ampacity) of each AWG size?
Approximate ampacity for copper wire in free air (60°C insulation): AWG 14 = 15A, AWG 12 = 20A, AWG 10 = 30A, AWG 8 = 40A, AWG 6 = 55A, AWG 4 = 70A, AWG 2 = 95A, AWG 1/0 = 125A, AWG 4/0 = 230A. These values decrease significantly when wires are bundled in conduit.
What is the resistance per foot/meter of common AWG sizes?
Copper resistance at 20°C: AWG 10 = 3.28 mΩ/m (1.0 mΩ/ft), AWG 12 = 5.21 mΩ/m (1.59 mΩ/ft), AWG 14 = 8.29 mΩ/m (2.52 mΩ/ft), AWG 18 = 20.9 mΩ/m (6.39 mΩ/ft), AWG 22 = 52.9 mΩ/m (16.1 mΩ/ft). Voltage drop = current × resistance × 2 (round trip).
What is the metric equivalent of AWG?
There is no exact match. Closest conversions: AWG 10 ≈ 6mm², AWG 12 ≈ 4mm², AWG 14 ≈ 2.5mm², AWG 16 ≈ 1.5mm², AWG 18 ≈ 1.0mm², AWG 20 ≈ 0.75mm², AWG 22 ≈ 0.5mm². IEC metric wire sizes (mm²) are used in Europe, Asia, and most of the world outside North America.
What is the difference between solid and stranded wire of the same AWG?
Same AWG = same total cross-sectional copper area = same DC resistance = same current capacity. But stranded wire is more flexible (better for cables that move) while solid wire holds its shape (better for permanent wiring in walls). Stranded wire has slightly larger overall diameter due to air gaps between strands.
What is 4/0 AWG?
4/0 (pronounced 'four-ought') is the largest standard AWG size: 11.68mm (0.46 inch) diameter, 107.2mm² area. The 'ought' sizes go: 1/0 (one-ought), 2/0, 3/0, 4/0. For sizes above 4/0, the MCM (thousand circular mils) or kcmil system is used: 250 MCM, 350 MCM, 500 MCM, etc.
How do I calculate voltage drop for a wire run?
V_drop = I × R_wire × 2 (the ×2 accounts for the return path). R_wire = resistance_per_meter × length. NEC recommends keeping voltage drop below 3% for branch circuits and 5% total. For a 20A load on 50 feet of AWG 12 copper: V_drop = 20 × 0.00159 × 100 = 3.18V (2.65% on 120V circuit).
What is the difference between copper and aluminum wire?
Aluminum has 61% of copper's conductivity, so aluminum wire must be 1-2 AWG sizes larger to carry the same current. AWG 10 copper ≈ AWG 8 aluminum for the same ampacity. Aluminum is lighter and cheaper but requires special connectors (anti-oxidant compound) to prevent corrosion at termination points.