Wire Gauge Calculator

This wire gauge calculator calculates the wire diameter, cross-sectional area, and resistance per unit length, given the AWG or SWG number. It works as an AWG calculator and SWG calculator.

In the rest of this article, we talk a bit more about:

• The different wire gauges the calculator uses;
• How to determine the wire gauges using the formulas and charts; and
• How to calculate wire resistance per unit length.

American wire gauge

American wire gauge (AWG) is a standardized wire gauge system used for the diameters of round, solid, nonferrous, electrically conducting wires. The AWG system consists of grades numbered from 0 to 40. The higher the grade number, the smaller the diameter of the wire. For example, a 12 AWG wire has a thicker diameter than a 14 AWG wire.

The formula for determining the diameter of an AWG number, $n$, is as follows:

For example, to calculate the diameter of a 36 AWG, we input $n = 36$ in the previous formula; for AWG 1, we input $n = 1$; and so on. The only exceptions are the lower gage numbers, in which we use the following $n$ values:

Standard wire gauge

The Standard wire gauge (SWG) is another standardized wire gauge system. It's not so popular these days, but it is still present when defining the thickness of guitar strings and some types of electrical wiring.

SWG doesn't follow an exact relationship like the one provided by the previous AWG formula (although some approximations exist). To obtain the diameter of a particular SWG, you need to look it up in a gauge chart:

Cross-sectional area

Once you know the wire diameter, you can calculate the cross-sectional area using the formula to calculate the area of a circle in terms of diameter ($d$):

The equation for the electrical resistance per unit length relies on the resistance-resistivity relationship found in our wire resistance calculator:

, where:

• $R$ — Resistance, in ohms $Ω$;
• $L$ — Wire's length, in meters ($\text m$);
• $\rho$ — Material's resistivity, in $Ω \cdot \text m$; and
• $A$ — Cross-section area, in $\text m^{2}$;

Rearranging for $R/L$ in the previous equation, we obtain the resistance per unit length:

So, to obtain the resistance per unit length, we need to know the resistivity of the material and the cross-sectional area (obtained with the wire gauge calculator).