Power Wire Gauge & Fuse
Choose the right power cable gauge and fuse for a car-audio amplifier based on current, length and voltage drop.
Inputs
Battery under load is usually 12–13 V.
From the battery fuse to the amp.
3% is the usual target; 5% is the maximum.
Voltage drop by gauge
Red = too much voltage drop. Yellow-brown (⚡<fuse) = the wire’s ampacity is lower than the recommended fuse.
| Gauge | Area | Drop | Ampacity |
|---|---|---|---|
| 16 AWG | 1.3 mm² | 7.09 V | 22 A |
| 14 AWG | 2.1 mm² | 4.46 V | 32 A |
| 12 AWG | 3.3 mm² | 2.81 V | 41 A |
| 10 AWG | 5.3 mm² | 1.76 V | 55 A |
| 8 AWG | 8.4 mm² | 1.11 V | 73 A |
| 6 AWG | 13.3 mm² | 0.70 V | 101 A |
| 4 AWG | 21.2 mm² | 0.44 V | 135 A |
| 2 AWG | 33.6 mm² | 0.28 V | 181 A |
| 1 AWG | 42.4 mm² | 0.22 V | 211 A |
| 1/0 | 53.5 mm² | 0.17 V | 245 A |
| 2/0 | 67.4 mm² | 0.14 V | 283 A |
| 3/0 | 85.0 mm² | 0.11 V | 328 A |
| 4/0 | 107.2 mm² | 0.09 V | 380 A |
How it works
Every wire has resistance. When a car-audio amp pulls tens or hundreds of amps, that resistance wastes power as heat and drops voltage before it reaches the amp, causing dimming lights, clipping and weak bass.
I_draw = P_rms / (efficiency × V) R_wire = ρ · L / A (ρ copper ≈ 0.0172 Ω·mm²/m) V_drop = I · R_wire Fuse ≈ 1.25 × I_draw (rounded up to a standard value)
The AWG standard defines conductor area from the gauge number: every 3 gauges halves the area, and every 6 gauges halves the diameter. Smaller numbers mean thicker cables. The calculator sizes the thinnest wire that satisfies both your voltage-drop limit and an ampacity check against the fuse.
The fuse must go within ~45 cm (18″) of the battery terminal; it protects the wire in case of a short, so never choose a fuse bigger than the wire’s ampacity. CCA (copper-clad aluminium) has about 32% more resistance than copper at the same size, so go up one or two gauges. The ampacity numbers are conservative chassis-wiring values for copper.
Average music draws only 1/8 to 1/4 of the peak current, see the Battery & Alternator calculator for what your electrical system can sustain.