Speaker Wire Gauge Calculator

Speaker wire gauge matters because wire has resistance, and too much resistance wastes power and degrades audio quality.

The goal: Keep wire resistance below 5% of speaker impedance (audiophile standard: below 2%).

Max Wire Resistance = Speaker Impedance × 0.05

Required Resistance per Foot = Max Resistance / (2 × Distance)

(Multiply distance by 2 because current flows through both conductors.)

AWG wire resistance (per foot at 20°C):

Quick guide (5% loss limit):

The power loss is not really the point

Work through the numbers and you find that even a badly undersized cable throws away a couple of decibels at worst, and a 5% loss is about 0.22 dB. Nobody can hear that. So why bother with thick cable at all?

Damping factor. The amplifier controls the woofer cone electrically, and it does that through the cable. Every ohm of series resistance between the amp and the voice coil weakens its grip on a cone that wants to keep moving after the signal stops. The cable puts a hard ceiling on it: speaker impedance divided by round-trip cable resistance. Keep the cable under 5% of the speaker impedance and that ceiling sits around 20, which is roughly where loose, woolly bass stops being audible. That, not wasted watts, is the reason a long run to a subwoofer wants 12 AWG.

Tips:

• Lower gauge number means thicker wire
• 4Ω speakers need thicker wire than 8Ω, because the same cable resistance is a bigger fraction of a smaller impedance
• Run both channels at the same length even if one speaker is closer, so the two sides match
• Use banana plugs or spade connectors for a connection that stays tight
• Oxygen-free copper is the normal stuff and it is fine. Exotic cables rarely change anything you can measure, let alone hear