🔌 Amplifier Wire Gauge Calculator
Size the power and ground wire for your amp from its RMS output or fuse rating and the length of the run — with the estimated current draw and a suggested inline fuse to protect the wire.
🔌 Recommended wire
Run the same gauge for power and ground, and fit an inline fuse within ~18 inches of the battery to protect the power wire. Round up (thicker wire = lower number) for high-output systems and long runs.
Feed the amp enough copper
An amplifier can only make the power its wiring will deliver. Too thin a power wire — or too long a run — starves the amp, drops voltage, dims your output, and can heat the cable dangerously. Sizing the gauge from the current draw and the run length is the difference between a clean, hard-hitting install and one that clips, gets hot, and trips into protection.
Use it with the Amplifier Power Calculator to estimate how much current your system will pull, and the Speaker Impedance Calculator to confirm the load that sets that draw.
❓ Frequently Asked Questions
How is the current draw estimated?
From the amplifier's RMS output, using I = totalRmsWatts ÷ (systemVoltage × efficiency), with 13.8 V (a running charging system) and 75% efficiency as defaults. So a 414 W RMS amp draws about 414 ÷ (13.8 × 0.75) = 40 A. If you'd rather, enter the amp's fuse rating directly and that current is used instead — the fuse is sized to the amp's real draw.
How is the wire gauge chosen?
Wire has to carry the current over the run length while keeping voltage drop low (roughly 4% at 13.8 V). This calculator multiplies current by run length to get 'amp-feet' and reads the gauge from a car-audio power-wire chart: up to 50 amp-feet uses 10 AWG, up to 100 uses 8 AWG, up to 300 uses 4 AWG, up to 600 uses 2 AWG, and above that 1/0 (0) AWG. Longer runs and higher current both call for thicker wire.
Should I use the same gauge for the ground wire?
Yes. The ground carries exactly the same current as the power wire, so it must be at least the same gauge. Keep the ground short — ideally under about 18 inches to clean, bare metal on the chassis — because a poor ground is one of the most common causes of weak output, noise, and amps dropping into protection.
What size fuse should I run, and where?
Fit an inline fuse on the power wire within roughly 18 inches of the battery — its job is to protect the wire (and car) if it shorts, not the amp. Size it to the wire's capacity and the amp's draw; this tool suggests the nearest common fuse at or above the estimated current. If you run multiple amps, a distribution block with individual fuses per amp is the tidy way to do it.