Speaker wire gauge chart by length and impedance: keep the cable under 5 % of the speaker’s ohms (about 0.42 dB). 16 AWG copper reaches 49 ft to an 8 Ω speaker; a 4 Ω speaker on 14 AWG reaches 39 ft. CCA wire has about 1.6× the resistance, so it runs about 40 % shorter.
05 · Speaker wire
GO HEAVIER:
16 AWG COPPER · 0.43 DB LOSS · 49 FT MAX (5 % RULE)
50 ft of 16 AWG copper adds 0.402 Ω out and back, 5.0 % of 8 Ω: you lose 0.43 dB, inaudible below about 0.5 dB.
Sort any column, print a shop sheet, download CSV. Click a row to load it in the calculator.
| Actions | |||||||
|---|---|---|---|---|---|---|---|
| 50 | 100 | 150 | 200 | 400 | 125 | ||
| 31 | 62 | 94 | 125 | 251 | 79 | ||
| 19 | 39 | 59 | 79 | 158 | 49 | ||
| 12 | 24 | 37 | 49 | 99 | 31 | ||
| 7 | 15 | 23 | 31 | 62 | 19 | ||
| 4 | 9 | 14 | 19 | 39 | 12 | ||
| 3 | 6 | 9 | 12 | 24 | 7 | ||
| 1 | 3 | 5 | 7 | 15 | 4 |
Copper resistance at 20 °C (10.371 Ω·cmil/ft). CCA column: ASTM B566 class 10A, 1.59 × the copper resistance.
| Actions | |||||||
|---|---|---|---|---|---|---|---|
| 122 | 244 | 366 | 488 | 976 | 307 | ||
| 76 | 153 | 230 | 307 | 614 | 193 | ||
| 48 | 96 | 145 | 193 | 386 | 121 | ||
| 30 | 60 | 91 | 121 | 242 | 76 | ||
| 19 | 38 | 57 | 76 | 152 | 47 | ||
| 12 | 24 | 36 | 48 | 96 | 30 | ||
| 7 | 15 | 22 | 30 | 60 | 19 | ||
| 4 | 9 | 14 | 19 | 38 | 11 |
Copper resistance at 20 °C (10.371 Ω·cmil/ft). CCA column: ASTM B566 class 10A, 1.59 × the copper resistance.
05 / Field guide
Speaker cable steals power by adding resistance in series with the speaker. Keep the out-and-back resistance under 5 % of the speaker’s nominal impedance and the loss stays near 0.4 dB, below what anyone hears; lower-impedance speakers need heavier wire for the same distance.
For a resistive load the speaker gets Z ÷ (Z + R) of the voltage, so the loss in decibels is 20·log10 of that. 5 % of Z is 0.42 dB; 12 % is 1 dB. 16 AWG copper to an 8 Ω speaker reaches 49 ft for 5 % and 121 ft for 1 dB.
loss dB = 20 · log10( Z ÷ (Z + R) ) R = 2 × L × r (Ω/ft) 5 % rule: R ≤ 0.05 × Z
Oxygen-free copper and ordinary annealed copper both sit at about 100 % IACS conductivity, so their resistance is the same for speaker runs; OFC’s case is corrosion and flexibility, not sound. Copper-clad aluminum is different: ASTM B566 class 10A conducts 62.9 % of copper, so it has 1.59 times the resistance of copper of the same gauge.
An amplifier’s damping factor is speaker impedance over its output impedance. Cable resistance adds to the output side, so a 200 DF amp into 8 Ω through 0.4 Ω of cable delivers a damping factor near 18 at the speaker; above about 10–20 the difference is hard to hear.
Speaker cable inside a wall or ceiling must be listed for it: look for a CL2 or CL3 marking (power-limited cable, NEC Article 722 in the 2023 edition). Ordinary zip cord is for exposed runs only. Through a fire-rated wall or a plenum, the cable needs the matching rating (CL2P or CMP).
Gauge matters most with low-impedance speakers. At 4 Ω the 5 % rule allows 24 ft of 16 AWG, 39 ft of 14 AWG and 62 ft of 12 AWG; at 8 Ω every figure doubles. Bi-wiring a speaker doubles the copper too, which halves the loop resistance.
Commercial background-music systems run their speaker lines at 70 V or 100 V through step-down transformers at each speaker. The current is small, so 16 or 18 AWG covers long runs that would need heavy cable at 8 Ω; those runs are sized by power and distance from the system maker’s tables, not by this chart.
Questions
For 8 Ω speakers, 16 AWG copper (good to about 49 ft by the 5 % rule). For 4 Ω, 14 AWG (39 ft) or 12 AWG.
For most home runs under 50 ft to 8 Ω speakers, yes. For 4 Ω speakers or longer runs go to 14 or 12 AWG; for in-wall runs use CL2 or CL3 rated cable.
It is not dangerous at speaker currents, but it has about 1.6 times the resistance of copper, so you need one gauge heavier (two AWG numbers lower) for the same loss.
Not because of its resistance, which equals ordinary copper’s. Gauge and length decide the loss.
Matching lengths keeps the two channels’ losses equal, but at these resistances a few feet of difference is inaudible. Use the longer run to choose the gauge for both.
It is listed for installation inside walls as power-limited cable. CL3 allows higher power than CL2. Without the marking, cable should stay exposed.
It halves the cable resistance, which matters only on long runs or very low-impedance speakers. A heavier single cable gives the same benefit.