Wire Gauge Calculator (AWG)
Look up the full specification of any AWG wire gauge — diameter in inches and millimetres, cross-sectional area in circular mils and mm², DC resistance per 1,000 feet, and NEC Table 310.16 ampacity at 60 °C, 75 °C, and 90 °C for both copper and aluminium conductors.
Diameter
2.05mm
Diameter
0.0808in
Area
3.31mm²
Area
6,530cmil
DC resistance
1.588Ω/1000ft
Ampacity @ 60 °C
20A
Ampacity @ 75 °C
25A
Ampacity @ 90 °C
30A
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Reading the AWG system
American Wire Gauge is a logarithmic scale. Every six gauges the diameter roughly halves, and every three gauges the cross-sectional area roughly halves. This means:
- 14 AWG has roughly half the area of 11 AWG
- 8 AWG has roughly twice the area of 11 AWG
- Each step from 14 to 12 to 10 roughly doubles the area (and ampacity)
Above 1 AWG, the system switches to "aught" (kcmil) sizes: 1/0 (one-aught), 2/0, 3/0, 4/0 — each progressively larger. Above 4/0, conductors are specified in kcmil (thousands of circular mils).
Common AWG sizes and their applications
- 14 AWG copper — 15 A lighting and general circuits (NEC 240.4(D))
- 12 AWG copper — 20 A receptacle and kitchen circuits
- 10 AWG copper — 30 A dryer, water heater, and AC circuits
- 8 AWG copper — 40–50 A ranges, EV chargers (Level 2)
- 6 AWG copper — 55–65 A ranges, subpanel feeds
- 4 AWG copper — 70–85 A feeders
- 2 AWG copper — 90–95 A service conductors
- 1/0 AWG copper — 150 A service entrance
- 2/0 AWG copper — 175 A service entrance
- 3/0 AWG copper — 200 A service entrance
Copper vs aluminium comparison
Aluminium conductors require a larger gauge than copper for equivalent ampacity. Approximate equivalents at 75 °C (NEC Table 310.16):
- 8 AWG copper (50 A) ≈ 6 AWG aluminium (50 A)
- 6 AWG copper (65 A) ≈ 4 AWG aluminium (65 A)
- 4 AWG copper (85 A) ≈ 2 AWG aluminium (75 A)
- 2 AWG copper (95 A) ≈ 1/0 AWG aluminium (120 A)
- 1/0 AWG copper (150 A) ≈ 3/0 AWG aluminium (155 A)
- 3/0 AWG copper (200 A) ≈ 350 kcmil aluminium (200 A)
Worked examples
Example 1 — dryer circuit:A 30 A clothes dryer at 240 V requires a dedicated circuit. At 75 °C, 10 AWG copper carries 35 A — sufficient. The conductor is protected by a 30 A breaker, which is less than the 35 A ampacity (NEC 240.4(B)).
Example 2 — voltage drop check:12 AWG copper has a DC resistance of 1.588 Ω per 1,000 ft. On a 50 ft one-way run (100 ft round-trip) at 20 A:
- Voltage drop = 20 × (100/1,000 × 1.588) = 3.18 V
- On a 120 V circuit: 3.18 ÷ 120 = 2.6% — acceptable for most loads
- On a 240 V circuit: 3.18 ÷ 240 = 1.3% — well within limits
Example 3 — service entrance sizing:A 200 A residential service uses 3/0 AWG copper (200 A at 75 °C) or 350 kcmil aluminium for the ungrounded conductors.
Who is this calculator for?
A quick reference for electricians, engineers, and electronics technicians who need AWG specifications at a glance — diameter, resistance, and ampacity — without looking up NEC tables. Particularly useful when specifying wire for automotive wiring, control panels, data cabling, EV charging circuits, and residential service entrance conductors. Also used when converting between AWG and metric (mm²) sizes for comparison with BS 7671 or AS/NZS cable tables.
Frequently Asked Questions
- What does AWG mean?
- AWG stands for American Wire Gauge. It is a standardised system where a smaller number means a larger conductor — 6 AWG is much thicker than 14 AWG. Each three-gauge step roughly doubles the cross-sectional area, and each six-gauge step roughly doubles the diameter.
- What is the difference between 60 °C, 75 °C, and 90 °C ampacity?
- These refer to the temperature rating of the conductor's insulation. Most breakers and terminals are rated for 60 °C or 75 °C connections, so NEC 110.14(C) limits you to those columns even if you're using 90 °C wire. The 90 °C column is only fully used when all connected equipment is also rated for 90 °C — common in some industrial applications.
- Why does resistance matter when choosing a gauge?
- DC resistance per 1,000 feet determines both heat generation and voltage drop. A larger gauge has lower resistance, carrying more current with less loss. For long runs, resistance is often the deciding factor — even if a smaller gauge has enough ampacity, voltage drop may require a larger size.
- Is copper or aluminium better for a given gauge?
- Copper has lower resistance for the same gauge, so it carries more current and produces less voltage drop. Aluminium is lighter and cheaper but needs to be approximately two sizes larger to match copper's ampacity. Aluminium also requires anti-oxidant compound at all connections and aluminium-rated terminations.
- What gauge is used for a 20 A circuit?
- NEC 240.4(D) requires 12 AWG copper (or 10 AWG aluminium) for 20 A branch circuits, regardless of the 75 °C ampacity of those conductors. This is the small-conductor protection rule that prevents undersized wire even when the load is light.
- How do I convert AWG to mm²?
- The conversion is: area (mm²) ≈ 53.5 ÷ 1.12^n, where n is the AWG number. Common conversions: 14 AWG ≈ 2.08 mm², 12 AWG ≈ 3.31 mm², 10 AWG ≈ 5.26 mm², 8 AWG ≈ 8.37 mm², 6 AWG ≈ 13.3 mm². Note that IEC/metric cable sizes do not map exactly — a 4 mm² cable is between 11 AWG and 12 AWG.
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