Amp fuse size: biggest fuse for each wire gauge
The fuse protects the wire, so it must be no bigger than the wire is rated for: up to 125 A on 4 AWG copper and 225 A on 1/0 copper. Then pick the size at or just above your amp’s full-power draw.
Put the main fuse within 18 inches of the battery positive. If the wire splits to thinner leads, fuse each lead for its own gauge.
Biggest fuse by wire gauge
Biggest fuse by wire gauge| AWG | Copper rating | Max fuse, copper | Max fuse, CCA |
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| 8 | 68 A | 60 A | 50 A |
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| 6 | 102 A | 100 A | 80 A |
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| 4 | 136 A | 125 A | 100 A |
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| 2 | 178 A | 175 A | 125 A |
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| 1 | 208 A | 200 A | 150 A |
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| 1/0 | 242 A | 225 A | 175 A |
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| 2/0 | 280 A | 250 A | 200 A |
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| 3/0 | 327 A | 300 A | 250 A |
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| 4/0 | 378 A | 350 A | 250 A |
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How to pick the fuse
Work out the amp’s full-power draw (RMS ÷ efficiency ÷ 13.8 V) and take the next standard fuse size up.
Check that fuse is no bigger than the wire’s maximum in the table. If it is, use thicker wire.
Ratings: 33 CFR 183.425 Table 5 (as ABYC E-11), 105 °C insulation, × 0.85 for the engine bay; CCA × 0.79. Fuse sizes are the standard ANL / AGU steps.
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.
Frequently asked questions
What size fuse for my amp wire?
The fuse protects the wire, so it must be no bigger than the wire can carry, and big enough not to blow at the amp’s full draw. Put it within 18 inches of the battery.
Can I use a bigger fuse than the amp needs?
Only up to what the wire is rated for. A fuse bigger than the wire’s rating lets the wire overheat before the fuse blows.
Do I still need the fuses on the amp?
Yes. The amp’s own fuses protect the amp; the fuse at the battery protects the wire. They do different jobs.