Car Audio & 12V Electrical
Amplifier Wire Gauge & Fuse Calculator
Estimate amplifier current draw, recommended OFC power wire gauge, fuse rating, and whether your charging system needs an upgrade.
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How to Use This Tool
- Set total system RMS watts for the amplifier(s) on the power wire.
- Choose system voltage (resting, running, or high-output).
- Select Class D or Class AB efficiency and cable run length.
- Use OFC for best conductivity; plan one size thicker if using CCA.
The Formula & Physics Behind the Math
Current (A) ≈ RMS watts ÷ (voltage × efficiency). Class D is modeled at ~80% efficiency and Class AB at ~65%. Recommended AWG and fuse size step up with current and longer trunk runs. Draws above ~120A typically warrant a Big 3 upgrade and high-output alternator.
Frequently Asked Questions
Should I use OFC or CCA wire?
Oxygen-free copper (OFC) carries current more efficiently and is preferred for high-power installs. Copper-clad aluminum (CCA) usually needs a thicker gauge for the same load.
Where should the fuse go?
Place the ANL (or equivalent) fuse on the positive cable within about 18 inches of the battery to protect the full run against short circuits.
What is a Big 3 upgrade?
Upgrading the battery positive, alternator charge, and engine ground cables to large OFC improves voltage stability when amplifiers draw heavy current.