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Hurrey's Automotive Wiring Sizing Tool – BETA
⚡ HURREY'S WIRING TOOL

Automotive Wiring Sizing Tool – BETA

Size copper vs aluminum wiring for automotive installs based on amps, run length and environment. Assumes stranded wire. Helps pick wire gauge, fuse, relay and switch strategy for lights, audio, inverters and more.

Stranded copper / aluminum Voltage drop sanity check Fuse & relay suggestions Example loads: lights, amps, inverters
Wire Size

Main Wiring Calculator

Pick load, run length, material and environment to get a starting gauge.

Stranded – 12V/24V Automotive
Use examples for quick ballparks, but always base final numbers on the manufacturer’s current rating.
Use the continuous current from the device spec sheet, not just a guess.
We’ll double this internally for round-trip (out + back ground).
Aluminum has higher resistance and lower ampacity for the same gauge.
Continuous loads get stricter drop limits and higher safety factors.
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Enter amps, length and environment to get a suggested minimum gauge and estimated voltage drop.

This is a sizing helper, not a code book. Always sanity check with proper tables and your own judgement.

Protection & Control

Fuse, Relay & Switch Suggestions

Built off the chosen load, not the wire rating.

Device-based
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Fuse selection will show here based on device amps and duty cycle.
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Relay and switch strategy will show here, including when to avoid running full load through a dash switch.

Rule of thumb: size fuses to protect the wire and the device, and size the wire for the worst-case current and environment. Device manufacturer always wins if their instructions conflict with this helper.

Wire & Material Info

AWG & Material Cheat Sheet

Very rough amps and notes for stranded automotive circuits.

Reference Only
Common stranded copper sizes
  • 18 AWG – short small circuits (up to ~10–12A typical).
  • 16 AWG – small lights, relays, control circuits (~15–20A).
  • 14 AWG – medium lights, fans, pumps (~25–30A).
  • 12 AWG – higher draw lighting, small inverters, fans (~35–45A).
  • 10 AWG – big fans, small audio, moderate inverters (~50–60A).
  • 8–4 AWG – main feeds, audio, inverters, small winch feeds.
  • 2–4/0 AWG – starters, winches, battery relocation, main grounds.
Copper vs aluminum
  • Aluminum has ~60% higher resistance than copper for the same gauge.
  • Aluminum also carries less current safely per gauge due to heating.
  • Always use lugs and hardware rated for aluminum and prep ends correctly.
  • Aluminum is usually only worth it for long, heavy primary runs – not small branch circuits.
Real World Loads

Typical Automotive Examples

Use as sanity checks next to the manufacturer’s numbers.

Brands: Baja / KC / Diode / etc.
Lighting
  • Small pair of LED pods: ~3–6A total at 13.5V.
  • Medium pair of high-output LEDs: ~8–12A.
  • 20–30" single row light bar: ~8–15A.
  • 40"+ high-power bar / full bumper package: ~20–30A.
  • Mixed lighting (rock + chase + pods): add up each circuit separately.
Other devices
  • Head unit + small speakers: ~5–10A.
  • Audio amps: roughly (watts ÷ 10) for 12–14V systems at full tilt.
  • On-board air compressor: ~25–40A depending on model.
  • Inverters: (watts ÷ 11) is a quick-and-dirty amps estimate.
  • Winches and starters: spike currents can be 300A+ – always follow their wiring charts.
Read This

Wiring Disclaimer – Automotive Only

This tool is aimed at low-voltage automotive-style systems (12–24V) using stranded wire. Values are approximate and based on simplified ampacity and voltage drop assumptions. They are not a replacement for wiring code, OEM service information or the instructions provided by lighting, audio, winch or inverter manufacturers.

Under-hood heat, bundling, poor grounds, connectors, terminals and installation quality all make or break a circuit. Always confirm wire size, fuse size and routing against the actual product documentation and your own professional judgement. If you’re not sure, oversize the wire, protect it properly and ask for help before letting the smoke out.

Summary

Session Summary / Wiring Notes

Copy this into your RO, install sheet or customer message.

Built off current inputs

Start filling in load, length and material – this will auto-populate with your selections and recommendations.

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