Wire Awg Chart

American Wire Gauge (AWG) sizes run backwards — the bigger the number, the thinner the wire — and each step changes the cross-section by about 26%. This chart lists the gauges from 4/0 to 24 AWG with diameter, area, resistance and typical copper ampacities, explains what each size is commonly used for, and describes a pack with printable charts and a voltage-drop worksheet.

AWG wire size chart

Diameters are for solid round wire from the standard AWG formula; stranded wire of the same gauge has a slightly larger overall diameter. Resistance is for copper at 20 °C and rises by about 0.4% per °C.

Typical copper ampacity (building wire)

These values follow the widely used US National Electrical Code table for copper conductors with not more than three current-carrying conductors in a raceway or cable at 30 °C ambient. Other rules limit how they are used — for example, overcurrent protection for 14, 12 and 10 AWG copper is typically limited to 15, 20 and 30 A — and corrections apply for temperature, bundling and the terminal ratings of connected equipment. Always follow the code in force where you are and the equipment instructions; electrical work may require a licensed electrician.

How AWG numbers work

AWG comes from the number of drawing steps used to make the wire. Every 6 gauges, the diameter halves; every 3 gauges, the cross-sectional area (and conductance) roughly halves; and each single gauge changes the area by about 26%. Sizes larger than 1 AWG are written 1/0, 2/0, 3/0 and 4/0 (“one aught” to “four aught”), and above 4/0, wire is sized in kcmil (thousands of circular mils). Outside North America, cables are usually sized directly by cross-section in mm² — 1.5, 2.5, 4, 6, 10 mm² and so on.

Voltage drop

Long runs lose voltage in the wire. For a single-phase circuit, voltage drop ≈ 2 × one-way length × current × resistance per unit length. A common design goal is to keep voltage drop under about 3% on a branch circuit and 5% overall. Example: a 20 A load 100 ft from the panel on 12 AWG copper (about 1.59 Ω per 1,000 ft) drops 2 × 100 × 20 × 0.00159 ≈ 6.4 V — about 5.3% on 120 V, which suggests stepping up to 10 AWG (about 4 V, 3.3%).

Worked example: choosing a wire size

An electrician plans a 30 A, 240 V circuit for a water heater 40 ft from the panel. The ampacity table points to 10 AWG copper at 30 A with 60 °C terminations. Voltage drop is 2 × 40 × 30 × 0.000999 ≈ 2.4 V — 1% of 240 V — well within the usual target, so 10 AWG is suitable, subject to the local code and the heater’s instructions. For a 150 ft run to a detached garage, voltage drop would push the choice up a size or more.

Copper vs aluminium

Aluminium conductors have about 61% of the conductivity of copper, so an aluminium wire must be roughly two AWG sizes larger to carry the same current. Aluminium is common for large service and feeder cables because it is lighter and cheaper; it needs connectors and terminals rated for aluminium and correct installation to avoid loose connections.

What’s in the pack

• Printable AWG chart (diameter, area, resistance) for 4/0 to 30 AWG
• Copper ampacity reference card with circuit examples
• AWG to mm² conversion card
• Excel voltage-drop calculator and wire-size checker
• Circuit planning worksheet

Printables fit US Letter and A4; the spreadsheet opens in Excel and Google Sheets.

AI-assisted content

Charts were generated from the standard AWG formula and reviewed by Kedop. They are reference information, not a substitute for the applicable electrical code.