What gauge power wire, ground wire, and fuse does your amplifier actually need? Enter your total RMS watts and how long the cable run is. Sized for voltage drop, not guesswork, with speaker wire sizing below.
Recommended OFC power wire for a Class D system, by total RMS watts and one-way cable length. Class AB or CCA: go one size larger, or just run the calculator above with your real numbers.
| Total RMS | 10 ft run | 15 ft run | 20 ft run |
|---|---|---|---|
| 300 W | 10 AWG | 8 AWG | 8 AWG |
| 500 W | 8 AWG | 6 AWG | 6 AWG |
| 1,000 W | 4 AWG | 4 AWG | 2 AWG |
| 1,500 W | 2 AWG | 2 AWG | 1 AWG |
| 2,000 W | 2 AWG | 1 AWG | 1/0 AWG |
| 3,000 W | 1/0 AWG | 2/0 AWG | 4/0 AWG |
Every foot of wire resists current a little. Too thin a cable over too long a run and the voltage sags exactly when the bass hits hardest, so the amp makes less power and the wire turns the difference into heat. This guide sizes cable to hold drop to roughly three quarters of a volt at full rated draw, and real music almost never pulls rated draw continuously.
Current makes a round trip. A fat power cable with a skinny or corroded ground is still a skinny circuit. Run the ground the same gauge as the power wire, keep it short, and land it on clean bare metal with a solid bolt.
Copper-clad aluminum costs less because it conducts less, roughly 60 to 70 percent of an equal gauge of oxygen-free copper, and the cut ends corrode faster in a car environment. It can work if you upsize it, which this guide does automatically. For big power or long runs, OFC is money well spent.
Every aftermarket radio uses the same colors on its own harness. This is the code for the radio side only. Your vehicle's side uses different colors, and matching function to function is the whole job: the radio's Yellow constant goes to your vehicle's constant wire, whatever color that happens to be. Need your vehicle's colors? That is exactly what the Wire Color Finder is for.
| Function | Radio-side wire | Notes |
|---|---|---|
| Constant 12V+ (memory) | Yellow | Always hot, keeps presets and clock |
| Switched 12V+ (accessory) | Red | Hot only with the key on |
| Ground | Black | Chassis ground |
| Illumination / dimmer | Orange/White | Sometimes solid Orange |
| Power antenna | Blue | Only live on radio tuner on some units |
| Amplifier remote turn-on | Blue/White | To your amp's remote terminal, not the antenna wire |
| Left front speaker + / - | White / White-Black | |
| Right front speaker + / - | Gray / Gray-Black | |
| Left rear speaker + / - | Green / Green-Black | |
| Right rear speaker + / - | Purple / Purple-Black |
The wire, not the amp. If the power cable ever shorts to the body anywhere along its run, that fuse blows before the cable overheats. That is why it is sized to the cable, and why it belongs within about 18 inches of the battery terminal. Your amplifier has its own internal protection for itself.
No. The ground carries the same current back to the battery, so it should be the same gauge. Keep it as short as practical and bolt it to clean, bare metal.
Many budget kits are optimistic, and some rate their wire by jacket size rather than actual conductor. If the kit wire is CCA sold as a copper size, it may be two effective sizes under. When a kit and this guide disagree, the guide is the conservative answer, and conservative is what you want on a cable carrying 100 amps through your car.
No. Treat this as a planning guide. Always follow the wire and fuse ratings printed by your amplifier and cable manufacturers, and local electrical codes where they apply.
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This amp wire sizing guide is one of 11 free tools in the Pistons & Ink Digital Toolbox, built for the aftermarket auto industry. If it helped you, the rest of the toolbox is right here.
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