Wire Gauge / AWG Calculator
Select an AWG gauge to see its diameter, cross-sectional area, ampacity, and resistance per meter for both copper and aluminum conductors.
Reviewed by the ToolNestr Editorial Team — July 2026
What different wire gauge capacity ranges mean
Thicker wires (lower AWG numbers) carry more current. Here are typical ampacity ratings for common copper wire sizes at 60\u00b0C insulation.
Electrician
Select the right wire gauge for residential and commercial installations based on load calculations and NEC ampacity tables.
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Solar Installer
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Hobbyist
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| AWG | Diameter (mm) | Area (mm\u00b2) | Ampacity Cu (A) | Ampacity Al (A) |
|---|---|---|---|---|
| 0000 | 11.684 | 107.20 | 230 | 180 |
| 000 | 10.404 | 85.00 | 200 | 155 |
| 00 | 9.266 | 67.40 | 175 | 135 |
| 0 | 8.251 | 53.50 | 150 | 120 |
| 1 | 7.348 | 42.40 | 130 | 100 |
| 2 | 6.544 | 33.60 | 115 | 90 |
| 4 | 5.189 | 21.20 | 85 | 65 |
| 6 | 4.115 | 13.30 | 55 | 40 |
| 8 | 3.264 | 8.37 | 40 | 30 |
| 10 | 2.588 | 5.26 | 30 | 25 |
| 12 | 2.053 | 3.31 | 20 | 15 |
| 14 | 1.628 | 2.08 | 15 | 10 |
| 16 | 1.291 | 1.31 | 10 | 5 |
| 18 | 1.024 | 0.82 | 5 | 3 |
| 20 | 0.812 | 0.52 | 3.5 | 2 |
| 22 | 0.644 | 0.33 | 2 | 1 |
| 24 | 0.511 | 0.20 | 1 | 0.5 |
| 26 | 0.405 | 0.13 | 0.5 | 0.25 |
| 28 | 0.321 | 0.08 | 0.3 | 0.15 |
| 30 | 0.255 | 0.05 | 0.2 | 0.1 |
| 32 | 0.202 | 0.03 | 0.15 | 0.05 |
| 34 | 0.160 | 0.02 | 0.1 | 0.03 |
| 36 | 0.127 | 0.01 | 0.05 | 0.02 |
| 38 | 0.101 | 0.01 | 0.03 | 0.01 |
| 40 | 0.080 | 0.01 | 0.02 | 0.005 |
How to use the Wire Gauge Calculator
Select wire size and material
Choose the AWG gauge from the dropdown and select copper or aluminum. The chart shows all standard sizes for comparison.
Set length and test current
Enter the conductor length and expected load current to compute voltage drop and power loss for your specific run.
Review the results
Check diameter, cross-sectional area, resistance, ampacity, voltage drop, and power loss. Adjust gauge if drop exceeds your limit.
Tips for wire gauge selection
Bigger number = thinner wire
AWG is counter-intuitive: 18 AWG is thinner than 12 AWG, which is thinner than 6 AWG. The scale goes backward \u2014 smaller numbers mean thicker conductors.
Always derate for bundling
When multiple current-carrying conductors are bundled together, heat dissipation is reduced. The NEC requires derating to 80% for 4\u20136 conductors, 70% for 7\u20139, and so on.
Consider voltage drop for long runs
Ampacity alone is not sufficient for long wire runs. Even if a wire can carry 30 A safely, the voltage drop over 200 ft at 120 V may exceed the recommended 3% limit.
Match insulation to environment
THHN (90\u00b0C) is common for dry locations, while XHHW (90\u00b0C wet) is better for outdoor or damp environments. Higher temperature ratings allow higher ampacity for the same gauge.
How AWG works
The American Wire Gauge (AWG) system is a standardized logarithmic scale used to designate wire diameters. Each successive gauge number corresponds to a 26% decrease in diameter. The system was originally based on the number of drawing operations needed to produce a given wire size, with higher numbers requiring more passes through smaller dies.
Key formulas
The diameter of an AWG wire can be calculated as: dn = 0.127 × 92(36-n)/39 mm. The cross-sectional area doubles every 3 AWG steps (e.g., 10 AWG has half the area of 7 AWG). Resistance per unit length depends on the material resistivity and area: R = ρ / A.
Ampacity derating
Ampacity values shown are for single conductors in free air at 30\u00b0C ambient with 60\u00b0C insulation. In practice, derating factors apply: ambient temperature above 30\u00b0C, more than three current-carrying conductors in a cable or conduit, and insulation type with higher temperature ratings all affect the safe operating current.
Why voltage drop matters at scale
In large installations, voltage drop is both a performance and economic consideration. The power lost as heat in wiring (I\u00b2R losses) can be substantial \u2014 a 200 A feeder with 2% drop loses 4 kW continuously. Upsizing wire reduces these losses and often pays for itself in energy savings over time.
Worked example
Frequently asked questions
What is AWG?
AWG stands for American Wire Gauge, a standardized wire sizing system used primarily in North America. Smaller AWG numbers indicate thicker wires with higher current capacity, while larger numbers indicate thinner wires.
How does AWG wire sizing work?
AWG uses a logarithmic scale where each step represents a 26% change in diameter. A decrease of 3 AWG sizes (e.g., from 10 AWG to 7 AWG) doubles the cross-sectional area. A decrease of 10 AWG sizes (e.g., 10 AWG to 1 AWG) multiplies the area by about 10.
What is ampacity?
Ampacity is the maximum current a wire can carry continuously without exceeding its temperature rating. It depends on the conductor material, insulation type, ambient temperature, and bundling with other wires.
Why does copper have higher ampacity than aluminum?
Copper has about 40% lower electrical resistance than aluminum for the same cross-sectional area. This means copper wires generate less heat for the same current, allowing them to carry higher currents safely.
What happens if I use wire with insufficient ampacity?
Using wire that is too thin for the current causes excessive heating, which can damage insulation, create fire hazards, and cause voltage drop issues. Always size wire for at least 125% of the expected continuous load.
Does wire length affect ampacity?
No, ampacity is a property of the wire itself and its installation conditions, not the length. However, longer runs increase voltage drop, which may require upsizing the wire even if ampacity is adequate.
What is the difference between stranded and solid wire?
Stranded wire consists of multiple small strands twisted together, making it more flexible and resistant to breakage from vibration. Solid wire is a single conductor, cheaper and easier to terminate, but less flexible.
How does temperature affect wire gauge selection?
Higher ambient temperatures reduce a wire's ampacity. The NEC provides correction factors for temperatures above 30°C (86°F). At 40°C, a wire rated for 30A may only be good for about 24A.
What is the largest AWG size?
The largest standard AWG size is 0000 (4/0), which is about 11.7 mm in diameter and can carry up to 230A for copper. Larger conductors are measured in kcmil (thousands of circular mils) rather than AWG.
Can I mix aluminum and copper wires?
Direct contact between aluminum and copper can cause galvanic corrosion. When connecting them, use approved connectors rated for both metals, and apply anti-oxidation compound. Many modern panels use copper for branch circuits.
Sources & references
This tool uses standard formulas and reference values from:
- • NFPA 70 — National Electrical Code (NEC), conduit fill, box fill and conductor ampacity. nfpa.org
- • IPC-2221, Generic Standard on Printed Board Design (trace width / current). ipc.org
- • NIST reference constants and unit definitions; IEEE standards where applicable. nist.gov
For educational and preliminary use. Verify against full engineering calculations and the governing standard before any real design.