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The American Wire Gauge (AWG) system numbers wires so that a smaller number means a thicker wire. Each 3 gauge steps roughly halves or doubles the cross-section area. From the gauge you can find the diameter, area, resistance, and an estimate of how much current the wire can safely carry (its ampacity).
| Quantity | Formula |
|---|---|
| Diameter | d = 0.127 × 92(36−AWG)/39 mm |
| Cross-section area | A = π/4 × d² |
| Resistance per metre | R/m = ρ / A |
| Estimated ampacity | I ≈ J × A (J = current density) |
Note: real ampacity depends on the insulation rating, ambient temperature, grouping, and the wiring standard. The current-density estimate here is a quick guide — always confirm against the applicable electrical code for safety-critical work.
American Wire Gauge, a standard numbering for wire sizes. A lower number means a thicker wire; each 3 gauges is about a factor of two in cross-section area.
First find the diameter, d = 0.127 × 92^((36−AWG)/39) mm, then the area A = π/4 × d². This calculator does both for you.
The maximum continuous current a conductor can carry without overheating. It depends on the wire size, insulation temperature rating, ambient conditions, and how the cable is installed.
It is a quick estimate from a current density (A/mm²). Real code ampacity can differ, so treat this as a starting point and verify against the electrical standard for safety-critical work.
Roughly 4 A/mm² for continuous power wiring, 6 A/mm² for general use, and up to 8 A/mm² for short chassis runs or intermittent loads. Lower is safer/cooler.
The gauge originally counted the number of drawing operations to make the wire — more draws made it thinner and gave a higher number. So 4/0 (very thick) is far bigger than 24 AWG.
These are the sizes below 1 AWG, written as 1/0, 2/0, 3/0, 4/0. In formulas they correspond to AWG 0, −1, −2, −3 — enter them as those numbers here.
Resistance per metre sets the voltage drop and I²R heating over a run. For long cables, check the voltage drop separately — a wire can be thick enough for ampacity but still drop too much.
Copper carries more current per mm² and is easier to terminate; aluminium is lighter and cheaper for large feeders but needs a size or two larger and special connectors.
Yes — higher temperature-rated insulation lets the same conductor carry more current. Ampacity tables are given per insulation type for this reason.
Grouping cables together traps heat, so each must be derated. The more conductors bundled, the lower the safe current per wire.
As a common rule, 14 AWG copper for 15 A and 12 AWG copper for 20 A branch circuits — but always follow your local wiring code.
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