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AWG Overview

A Guide to American Wire Gauge (AWG)

This guide provides a comprehensive overview of the American Wire Gauge standard, explains the core principles behind its measurements, and offers a set of tools to help you determine the correct gauge for your specific needs.

1. What is American Wire Gauge?

American Wire Gauge, commonly referred to by its acronym AWG, is the standardised system used in North America for measuring the diameter of solid, round, non-ferrous electrical wires. It is also known as the Brown & Sharpe (B & S) Wire Gauge.

The most important concept to understand about the AWG system is its inverse relationship: as the gauge number increases, the diameter of the wire decreases. For example, a 24 AWG wire is thinner than an 18 AWG wire. This is because the gauge number originates from the number of drawing dies a wire must pass through during the manufacturing process; more passes result in a thinner wire and a higher number.

The AWG scale is logarithmic, not linear. This means that the change in diameter between consecutive gauge sizes is a constant ratio. This standardised, mathematical progression allows for consistent and predictable electrical properties across the entire range of wire sizes.

2. Understanding the AWG Scale: Key Rules of Thumb

Because the scale is logarithmic, a few simple rules of thumb can help you quickly estimate a wire's properties without needing complex formulas. These are particularly useful for comparing two different wire gauges.

Electrical Resistance

  • Halving/Doubling: A change of 3 AWG numbers approximately doubles or halves the electrical resistance. For instance, a 20 AWG wire has roughly double the resistance of a 17 AWG wire.
  • Factor of 10: A change of 10 AWG numbers changes the resistance by a factor of approximately 10. A 30 AWG wire has about 10 times the resistance of a 20 AWG wire.

Physical Diameter

  • Halving/Doubling: A change of 6 AWG numbers approximately doubles or halves the wire's diameter. For instance, a 12 AWG wire has roughly twice the diameter of an 18 AWG wire.
  • Factor of 10: A change of 20 AWG numbers changes the diameter by a factor of approximately 10. A 22 AWG wire has about one-tenth the diameter of a 2 AWG wire.