Speaker wire is one of the few parts of an audio system where the right answer can be worked out with simple arithmetic. Too thin a wire wastes amplifier power as heat and loosens the amplifier's control over the woofer; going far thicker than needed just costs money and makes the wire harder to route. This guide shows you how to choose the gauge for your run length and speaker impedance, and what actually matters beyond the number on the spool.
AWG (American Wire Gauge) is a size scale where smaller numbers mean thicker wire. Every three steps down the scale roughly doubles the copper cross-section and halves the resistance. So 13 AWG has about half the resistance of 16 AWG, and 10 AWG about half that of 13 AWG.
Approximate resistance of solid-copper-equivalent wire at room temperature:
| Gauge | Ohms per 1,000 ft (one conductor) | Typical use |
|---|---|---|
| 18 AWG | ≈ 6.4 | Short runs to small speakers, tweeters |
| 16 AWG | ≈ 4.0 | Car door speakers, short home runs |
| 14 AWG | ≈ 2.5 | Most home and PA runs up to medium length |
| 12 AWG | ≈ 1.6 | Long PA runs, subwoofers, low-impedance loads |
| 10 AWG | ≈ 1.0 | Very long runs or 2-ohm and lower loads |
Remember that a speaker circuit has two conductors, so the total loop resistance is twice the one-way length. A 25 ft run uses 50 ft of copper.
A widely used guideline is to keep the total wire resistance below about 5% of the speaker's nominal impedance. At that level the power lost in the wire is small and the amplifier's damping is barely affected. The formula:
Loop resistance = (one-way length in ft × 2 ÷ 1,000) × ohms per 1,000 ft
Worked example: a single 8-ohm PA speaker 50 ft from the amplifier. 5% of 8 ohms is 0.4 ohm. With 16 AWG: 100 ft × 4.0 / 1,000 = 0.40 ohm — right at the limit. With 14 AWG: 0.25 ohm — comfortably inside. Choose 14 AWG.
Same run, 4-ohm load (for example two 8-ohm cabinets in parallel at the end of one cable): the limit drops to 0.2 ohm, so 12 AWG (0.16 ohm) is the better choice. Halving the impedance halves the length you can run on a given gauge.
Derived from the 5% guideline above (one-way distance):
| Gauge | 8-ohm load | 4-ohm load | 2-ohm load |
|---|---|---|---|
| 18 AWG | up to ~30 ft | up to ~15 ft | up to ~8 ft |
| 16 AWG | ~50 ft | ~25 ft | ~12 ft |
| 14 AWG | ~80 ft | ~40 ft | ~20 ft |
| 12 AWG | ~125 ft | ~60 ft | ~30 ft |
| 10 AWG | ~200 ft | ~100 ft | ~50 ft |
These are guidelines, not hard limits. Exceeding them a little will not damage anything; it just costs a bit of output and bass tightness.
Passive PA speakers often sit 50–100 ft from the amplifier, so 14 AWG is a practical minimum and 12 AWG is common. Use proper speaker cable, never instrument cable (thin, shielded cable made for low-level signals). Twist-lock speaker connectors make the connection secure and keep speaker cables from being plugged into line inputs by mistake; see our twist-lock connector wiring guide.
Copper wire resistance per 1,000 feet is a published property of each gauge. Approximate values for solid/stranded copper at room temperature:
| AWG | Ohms per 1,000 ft (approx.) |
|---|---|
| 18 | 6.4 |
| 16 | 4.0 |
| 14 | 2.5 |
| 12 | 1.6 |
| 10 | 1.0 |
Signal travels out on one conductor and back on the other, so the length that counts is twice the run. Total wire resistance = (2 × run in feet ÷ 1,000) × ohms per 1,000 ft. Compare that to the 5% target (0.05 × speaker impedance).
This is why the chart changes so much with impedance: halving the load impedance halves the wire resistance you can tolerate.
| Situation | Starting point | Notes |
|---|---|---|
| Bookshelf speakers, short runs, 8 ohms | 16 AWG | Thicker costs little more; fine if it fits the terminals |
| In-wall or long home runs | 14 or 12 AWG, in-wall rated | Check local code for the jacket rating (e.g. CL2/CL3) |
| Car door speakers on a head unit | 16 or 18 AWG | Short runs, low power; door boot flex matters more than gauge |
| Car subwoofer from an amp | 12 or 14 AWG | Low impedance loads (2 ohms or less) need heavier wire |
| Stage PA, 4-ohm cabinets, 50 ft+ | 12 AWG or heavier | Use rugged, flexible jacketed cable rated for stage use |
Many low-cost cables are copper-clad aluminum. Aluminum has higher resistance than copper, so a CCA cable behaves roughly like copper wire about two gauges thinner. If you buy CCA, step up in size, or choose oxygen-free or plain stranded copper and use the chart as written. CCA is also more brittle at repeated bends, which matters in car doors and on stage.
Lower resistance never hurts, but once loss is under a few percent of the speaker impedance, further gains are inaudible in practice. Thicker wire also costs more and is harder to fit into terminals.
Yes for tweeters and short runs to 4-ohm door speakers. For subwoofers or runs over about 15 ft, step up to 16 or 14 AWG.
No. Arrows printed on some cables are marketing; what matters is keeping positive and negative consistent at both ends.
For a typical car install with a short run, 12 or 14 AWG. For longer runs, use the formula above and aim for under 0.1 ohm of loop resistance.
Shopping for speakers to wire up? Browse our 6" coaxial door speakers, 12" car subwoofer, or 4-pole twist-lock speaker connectors.