What size wire do I need?Updated 3 hours ago
Amplifier Wire Size Guide
What Size Power and Ground Wire Do I Need for My Amplifier?
To operate correctly, an amplifier needs power and ground wiring large enough to handle the system's electrical current. Choosing the correct wire gauge depends on your amplifier's current draw (in amperes) and the length of the wire between your battery and the amplifier.
Use the formulas below to calculate current draw, then refer to the chart to select the appropriate wire size.
How to Calculate Current Draw
- Find RMS Power Output: Multiply the number of channels by the RMS watts per channel. Add totals if using multiple amps.
- Use the Right Formula:
- Class D Amp:
Current Draw = Total RMS Watts ÷ 0.75 ÷ 13.8 Volts - Class AB Amp:
Current Draw = Total RMS Watts ÷ 0.50 ÷ 13.8 Volts
- Class D Amp:
Note: If you're unsure of your amplifier class, use the Class AB formula to be safe.
Wire Gauge Chart (Copper Only)
| Amperes | 0–4 ft | 4–7 ft | 7–10 ft | 10–13 ft | 13–16 ft | 16–19 ft | 19–22 ft |
|---|---|---|---|---|---|---|---|
| 250–300 | 4 gauge | 2 gauge | 2 gauge | 1/0 gauge | 1/0 gauge | 1/0 gauge | 2/0 gauge |
| 200–250 | 4 gauge | 4 gauge | 2 gauge | 2 gauge | 1/0 gauge | 1/0 gauge | 1/0 gauge |
| 150–200 | 6 or 4 ga. | 4 gauge | 4 gauge | 2 gauge | 2 gauge | 1/0 gauge | 1/0 gauge |
| 125–150 | 8 gauge | 6 or 4 ga. | 4 gauge | 4 gauge | 2 gauge | 2 gauge | 2 gauge |
| 105–125 | 8 gauge | 8 gauge | 6 or 4 ga. | 4 gauge | 4 gauge | 4 gauge | 2 gauge |
| 85–105 | 8 gauge | 8 gauge | 6 or 4 ga. | 4 gauge | 4 gauge | 4 gauge | 4 gauge |
| 65–85 | 10 gauge | 8 gauge | 8 gauge | 6 or 4 ga. | 4 gauge | 4 gauge | 4 gauge |
| 50–65 | 10 gauge | 10 gauge | 8 gauge | 8 gauge | 6 or 4 ga. | 6 or 4 ga. | 4 gauge |
| 35–50 | 10 gauge | 10 gauge | 10 gauge | 8 gauge | 8 gauge | 8 gauge | 6 or 4 ga. |
| 20–35 | 12 gauge | 10 gauge | 10 gauge | 10 gauge | 10 gauge | 8 gauge | 8 gauge |
| 0–20 | 12 gauge | 12 gauge | 12 gauge | 12 gauge | 10 gauge | 10 gauge | 10 gauge |
Additional Notes
Automotive Voltage
While vehicles operate on 12-volt systems, the alternator typically runs around 13.8 volts. This is the value used in our formulas for more accurate real-world calculations.
Resistance Increases with Distance
Longer cable runs create more resistance, which can lead to voltage drops. Using thicker wire compensates for this resistance and helps maintain system performance.
Wire Size and Safety
Installing too small a gauge can result in power loss, system underperformance, and safety hazards. Larger gauge wiring can improve performance and reliability.
What Size Speaker Wire Should I Use?
- Speakers: 18, 16, or 14-gauge
- Subwoofers: 12, 8, or 4-gauge
Use larger wire for longer runs or higher power systems. For example, 14-gauge is ideal for 100W to the front speakers if the amp is in the trunk.