Enter an AWG wire size, conductor material, and run length to get the wire's diameter, cross-sectional area, total resistance, and weight.
Quick Facts
AWG diameter formula
d (mm) = 0.127 × 92^((36−AWG)/39)
Every 3-gauge decrease roughly doubles cross-sectional area; every 6-gauge decrease roughly doubles diameter.
Resistance basis
R = ρ × L ÷ A at 20°C (68°F)
Standard resistivity: copper 1.68×10⁻⁸ Ω·m, aluminum 2.65×10⁻⁸ Ω·m, for solid annealed conductors.
Results
Calculated
Wire Diameter
—
Conductor diameter for this AWG size
Cross-Sectional Area
—
Conductor area (mm² and circular mils)
Total Resistance
—
Resistance of the wire run at 20°C
Total Wire Weight
—
Bare conductor weight for the run
Ready
Enter an AWG size, material, and length, then press Calculate.
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How to use this calculator
Enter the wire's AWG size (American Wire Gauge), choose the conductor material (copper or aluminum), set the run length in feet, and choose whether that length is one-way or round-trip. Click Calculate to get the wire's diameter, cross-sectional area, total resistance, and total weight. Click Reset to return to the default 12 AWG copper example.
Understanding the inputs
AWG size accepts standard gauge numbers from 40 (fine, hair-thin wire) down to 0, and the "aught" sizes 1/0 through 4/0 are entered as -1 through -3. Conductor material sets the resistivity and density used for the resistance and weight calculations — copper and aluminum differ meaningfully on both. Run length is the physical distance the wire travels; choose round-trip if you want the resistance and weight of both the outbound and return conductor in a circuit (common for DC and single-phase AC runs).
Interpreting the results
Wire diameter and cross-sectional area are geometric properties of the AWG size alone and do not depend on length or material. Total resistance and total weight scale directly with the length you enter and depend on the material chosen — aluminum is roughly 1.6× more resistive but only about 30% the density of copper for the same size. This tool reports physical wire properties only; it does not determine safe current-carrying capacity (ampacity), which depends on insulation rating, ambient temperature, and installation method per electrical code tables.
Frequently Asked Questions
What does the AWG number mean?
AWG (American Wire Gauge) is a standardized numbering system for round conductor diameters. Confusingly, a smaller AWG number means a thicker wire: sizes run from 40 (hair-thin) down to 0 and then into the "aught" sizes 1/0, 2/0, 3/0, 4/0 (entered here as -1, -2, -3), which are the thickest common sizes. Each step follows a fixed geometric ratio, not a linear one.
What is the formula for AWG wire diameter?
Diameter in millimeters equals 0.127 times 92 raised to the power of (36 minus the AWG number) divided by 39: d(mm) = 0.127 × 92^((36−AWG)/39). This formula is exact by definition of the AWG standard. A useful shortcut: every 3-gauge decrease roughly doubles the wire's cross-sectional area, and every 6-gauge decrease roughly doubles its diameter.
How is the wire's resistance calculated?
Resistance uses R = ρ × L ÷ A, where ρ is the material's resistivity (about 1.68×10⁻⁸ Ω·m for annealed copper and 2.65×10⁻⁸ Ω·m for aluminum at 20°C/68°F), L is the conductor length in meters, and A is the cross-sectional area in square meters. Stranded wire, higher operating temperatures, and long-term corrosion all increase resistance slightly above this ideal solid-conductor value.
Does this tell me the right wire size for my amperage?
No. This calculator reports the physical properties of a given AWG size (diameter, area, resistance, weight), not safe current-carrying capacity. Ampacity depends on insulation type, ambient temperature, conduit fill, and installation method, and is set by tables in codes such as the NEC or IEC 60364. For circuit sizing, consult the applicable code table or a licensed electrician.