Speaker Wire Gauge & Length Calculator (Loss, Damping Factor & AWG)

How it works

R (round trip) = 2 × length × Ω/m of the gauge (18 AWG 0.0209, 16 AWG 0.0132, 14 AWG 0.0083, 12 AWG 0.0052, 10 AWG 0.0033 Ω/m) · loss dB = 20 log₁₀(Z ÷ (Z + R)) · power lost = P × R ÷ (Z + R) · 5% rule: R ≤ 0.05 Z · system damping = Z ÷ (Z/DF_amp + R)

Speaker wire is a resistor in series with the speaker, and everything it does follows from that: it drops a share of the amplifier's output as heat, it lowers the effective damping factor by adding resistance the speaker sees looking back at the amplifier, and because a speaker's impedance rises and falls with frequency, a resistive cable subtly reshapes the response — more loss where the impedance dips. Keeping the round-trip resistance below about five percent of the speaker impedance keeps all three effects under half a decibel, and since resistance falls with wire area, that rule turns directly into a maximum run for each gauge, halving for four-ohm speakers.

Worked example

A 15 m run of 16 AWG to an 8 Ω speaker has about 0.40 Ω round trip — 4.9% of the impedance, just inside the 5% rule — losing about 0.42 dB and 4.7 W of 100 W, with a system damping factor near 18. The same cable to 4 Ω speakers would be 9.9% and need 12 AWG; 16 AWG is fine to about 15 m at 8 Ω, 14 AWG to 24 m and 12 AWG to 38 m.

Frequently asked questions