Wire

Wire is a single electrical conductor that may or may not be insulated by a jacket. See Cable for multiple conductors housed within a single jacket.

Sizing

AWG

American Wire Gauge is the standard system for wire sizing used predominantly in North America. Wire sizes are logarithmically stepped, with a larger gauge signifying a smaller cross section. The formula for calculating diameter of a wire for standard and metric units is as follows:

$d_{n}=0.005~\mathrm {inch} \times 92^{\frac {36-n}{39}}=0.127~\mathrm {mm} \times 92^{\frac {36-n}{39}}$

Choosing Wire Gauge

Ampacity

Ampacity is the maximum current you can safely pass through the wire. This is important for determining what wire gauge to run. A larger gauge wire will be able to carry more current, but will be heavier.

Voltage Drop

Voltage drop is the reduction in voltage in a circuit from the source to the load. Since all wires have resistance, there will always be a difference in voltage from one end of a wire to another if current is flowing through it. If the voltage drops too low, electrical devices may not function properly. Since a larger gauge wire will have a smaller resistance per foot, going to a larger gauge wire decreases the voltage drop.

This is easily calculated with the formula Failed to parse (MathML with SVG or PNG fallback (recommended for modern browsers and accessibility tools): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle V = IR} , where V is the change in voltage, I is the current running through the wire, and R is the resistance of the wire. When choosing wire gauges, it might be a good idea to choose a fixed percentage voltage drop (say, 5%), and then choose all your wire gauges based on that.

Electrical Characteristics

Voltage Rating

Wire manufacturers will specify a voltage rating, which is the maximum voltage you can send through the wire. If the voltage rating is exceeded, the insulation could break down and cause a short circuit or a fire. The most common voltage rating seems to be 600V, but if you're working with high voltages this is worth double checking.