First determine the length of power cable required to run from the car battery to the amplifier, and then see the power wire gauge chart. Using the amperage rating given for the amplifier, find the correct gauge.

• The maximum amperage rating for the amplifier can be identified either by size of the fuse that is included with it, or the size recommended in the amplifier's manual.(If you are using multiple amplifiers wired through a distribution block or if your amp has multiple fuses, just add all of the values together.)
• When estimating the length of the cable needed to run from the battery to the amp, add 20% to account for the actual path that the wire will take when routed through the vehicle. For the "cable length" be sure to include the length of the amp's ground wire, which should be at least the same gauge as the power wire.
• To determine the amperage draw of you amplifier, multiply the total output of the amp by two, and divide this number by fourteen. For example: (amp is 100 watts by 2 channels) 200 times 2 = 400. 400 divided by 14 is 28.5 amps. The total current draw for this amp would be 28.5 amperes.