What gauge wire for a 500 watt amp?
A 500 W RMS class D amp draws about 45 A at full power. Fuse it at 50 A at the battery and run 6 AWG copper power and ground (or 4 AWG if the wire is CCA) for a 16 ft run.
A class A/B amp of 500 W draws more, about 72 A, and takes a 80 A fuse.
Power and ground wire gauge for a 500 W amp
Power and ground wire gauge for a 500 W amp| Power run | Class D copper | Class D CCA | A/B copper | A/B CCA |
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| 5 ft | 10 | 8 | 6 | 6 |
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| 10 ft | 8 | 6 | 6 | 4 |
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| 15 ft | 6 | 4 | 4 | 2 |
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| 20 ft | 6 | 4 | 4 | 2 |
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| 25 ft | 4 | 2 | 2 | 1 |
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Current draw and fuse for a 500 W amp
Current draw and fuse for a 500 W amp| Amp class | Current draw at full power | Fuse at the battery |
|---|
| Class D | 45 A | 50 A |
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| Class A/B | 72 A | 80 A |
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Good to know
Use the same gauge for the ground, as short as you can, to bare metal on the body or frame.
Several amps on one run: add their RMS watts. With a distribution block, each amp’s own lead can be thinner, with its own fuse.
Method: current at full power = RMS ÷ efficiency (class D 80 %, A/B 50 %) ÷ 13.8 V; the next standard fuse; the thinnest wire rated for that fuse (33 CFR 183.425 Table 5, 105 °C, × 0.85 for the engine bay; CCA × 0.79) with at most 0.5 V drop over the power run plus 3 ft of ground.
Guidance only, never a safety rating. Follow your amp and vehicle manuals. The fuse protects the wire: put it within 18 in of the battery. Disconnect the battery before you wire.
Wire gauge for other amp sizes
Frequently asked questions
What gauge wire do I need for a 500 watt amp?
A 500 W RMS class D amp draws about 45 A at full power. Fuse it at 50 A at the battery and run 6 AWG copper power and ground (or 4 AWG if the wire is CCA) for a 16 ft run.
What size fuse for a 500 watt amp?
About 50 A for class D, the next standard size above its full-power draw of 45 A, and never bigger than the wire is rated for.
Will my alternator keep up with a 500 watt amp?
At full power the amp alone draws about 45 A (class D), on top of the 40–60 A the vehicle uses. Music averages less; check yours with the current draw calculator.