Power and ground wire gauge, fuse size and Big 3 gauge for your amp: current draw from RMS watts, copper or CCA, voltage drop over your run.
Amp RMS power, total (W)
Add up every amp on this wire. RMS, not peak.
Amp class
Class
D
A/B
Class D
Class A/B
Class D
Class A/B
Wire
Copper
(OFC)
CCA
(aluminum)
Copper (OFC)
CCA (aluminum)
Copper (OFC)
CCA (aluminum)
Power wire length, battery to amp (ft)
Ground wire length (ft)
Keep it short, to bare metal on the body or frame.
Alternator output (A)
Optional, for the Big 3 gauge.
Power and ground wire
4 AWG
Fuse at the battery
100 A
Current draw at full power
91 A
Voltage drop over the run
0.43 V (3.1 % of 13.8 V)
Thinnest wire for the fuse alone
6 AWG
Biggest fuse for this wire
125 A
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.
How it works
Enter the total RMS power of the amps on the wire, the amp class, copper or CCA, and how long the power and ground runs are. You get the current draw, the fuse to put at the battery, and the gauge that carries that fuse with less than half a volt of drop.
Example: a 1,000 W RMS class D amp draws 1,000 ÷ 0.8 ÷ 13.8 = 90.6 A at full power. The fuse is 100 A. With 16 ft of power wire and 3 ft of ground, 4 AWG copper drops 0.43 V. In CCA the same run needs 2 AWG.
A 2,000 W class D amp draws 181 A: a 200 A fuse and 1 AWG copper at the same lengths. For the Big 3 with a 220 A alternator, use 1/0.
Frequently asked questions
What gauge wire for a 1,000 watt amp?
For a class D amp with about 16 ft of power wire: 4 AWG copper or 2 AWG CCA, with a 100 A fuse at the battery.
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.
Is CCA wire OK?
It works if you go bigger: CCA has about 60 % more resistance than copper, so it usually takes one or two sizes thicker.
Do I need the Big 3 upgrade?
Past about 1,000 W RMS, or if your lights dim on bass notes, it is the cheapest fix: it lets the alternator’s current reach the battery and the body.