How to Use Wire Solved: Complete Tutorial
This guide will walk you through using Wire Solved to get accurate wire sizing recommendations for your vehicle electrical projects.
Quick Start (60 Seconds)
- Enter your amp draw - Check device specs or measure with multimeter
- Enter wire run length - Measure from battery to device (one-way)
- Click Calculate - Get instant recommendations
- Done! - You now know what wire gauge and fuse to use
That’s it for basic use. But there’s more power in Advanced Settings…
Understanding the Inputs
Device/Load Name (Optional)
What it is: A label for your circuit
Why use it: Helps track multiple circuits when planning a build
Example: “Roof Light Bar”, “Rear Fridge”, “Winch”
Tip: If you’re planning a complete build, run calculations for each device and save screenshots with names for reference.
Amp Draw (Required)
What it is: The continuous current your device pulls
Where to find it:
- Device specifications (check manual or label)
- Multimeter measurement (device running)
- Online specs for your exact model
Important: Use continuous amp draw, not peak. A winch might peak at 400A but runs continuously at 150A.
Common Values:
- LED light bar (50"): 10-20A
- Fridge/freezer: 4-6A
- Inverter (1000W): 80-100A
- Winch (9000 lb): 150-200A continuous
- Air compressor: 15-30A
Tip: If you don’t know exact amperage, calculate it:
Amps = Watts / Volts
Example: 150W light / 12V = 12.5A
Wire Run Length (Required)
What it is: One-way distance from power source to device
How to measure:
- Use a tape measure or string
- Follow the actual path the wire will take
- Account for routing around obstacles
- Add a little extra (10%) for connections
Important: Enter ONE-WAY length only. Wire Solved automatically doubles it (power + ground) for calculations.
Example: If battery is in engine bay and device is 15 feet away in the rear, enter 15 feet, not 30.
Metric Option: Check “Use metric (meters)” to enter length in meters. Wire Solved converts automatically.
System Voltage (Fixed at 12V)
What it is: Your electrical system voltage
Current support: 12V only
Coming soon: 24V option
Advanced Settings Explained
Click “Advanced Settings” to access additional options:
Voltage Drop Tolerance
What it is: How much voltage loss you’ll accept
Options:
- Conservative (3%) - Sensitive electronics, long runs
- Standard (5% - Default) - Most accessories, industry standard
- Relaxed (10%) - Non-critical loads where dimming is acceptable
When to use Conservative (3%):
- GPS units
- Radios
- Sensitive electronics
- Any device where voltage stability matters
When to use Standard (5%):
- LED light bars
- Fridges
- Most accessories
- Default for general use
When to use Relaxed (10%):
- Work lights where brightness isn’t critical
- Backup systems
- Temporary installations
Tip: When in doubt, use Standard (5%). It’s the industry standard for a reason.
Load Type
What it is: How long the device runs
Options:
- Continuous - Runs for >3 hours (lights, fridge, accessories)
- Intermittent - Short bursts (winch, air compressor)
Why it matters: Affects fuse sizing. Continuous loads use 125% fuse sizing per electrical code (NFPA 70).
When to use Continuous:
- Anything that runs constantly or for extended periods
- LED light bars
- Fridges
- Inverters
- Chargers
- Interior lights
- When in doubt
When to use Intermittent:
- Winches (typically <10 min use)
- Air compressors
- Power tools
- Devices with duty cycle ratings
Tip: If unsure, choose Continuous. It’s safer.
Understanding the Results
After calculating, Wire Solved shows:
Recommended Wire Gauge
Example: “6 AWG”
This is the minimum wire gauge that:
- Can safely handle your amperage
- Keeps voltage drop under your tolerance
- Won’t overheat during operation
What to buy: Stranded copper automotive wire in this gauge or thicker.
Wire Capacity
Example: “This wire safely handles up to 65A continuous”
This shows the maximum current rating for the recommended wire, so you understand the safety margin.
Fuse Size
Example: “25A”
This is:
- The nearest standard fuse size
- Sized to protect your wire from overcurrent
- Includes 125% buffer for continuous loads (or 100% for intermittent)
What to buy: Standard automotive fuse in this rating (blade fuse for <40A, ANL for higher current).
Voltage Drop
Example: “0.32V (2.6%)”
This shows:
- Actual voltage loss over your wire run
- Percentage of system voltage
- Status indicator (optimized / near limit / high)
Green (✓ Optimized): Voltage drop is well under your tolerance
Yellow (⚠️ Near Limit): Close to tolerance, consider next gauge up
Red (⚠️ High): Exceeds tolerance, wire upgrade needed
Safety Check
Example: “Based on your 20A load, 12 AWG would handle the current, but we upgraded to 10 AWG to keep voltage drop under 5% for your 20-foot wire run.”
This explains:
- Why Wire Solved chose this gauge
- Whether it was upgraded due to voltage drop
- That your wire is both safe and efficient
Common Scenarios
Scenario 1: Roof Light Bar
Inputs:
- Amp Draw: 12A
- Wire Length: 18 feet (roof to battery)
- Voltage Tolerance: Standard (5%)
- Load Type: Continuous
Results:
- Wire: 14 AWG or 12 AWG (depending on voltage drop)
- Fuse: 15A
- Explanation: May upgrade from 16 AWG to control voltage drop
Shopping List:
- 40 feet of 14 AWG stranded copper wire (20 ft power + 20 ft ground)
- 15A blade fuse
- Inline fuse holder
- Ring terminals and connectors
Scenario 2: Rear-Mounted Fridge
Inputs:
- Amp Draw: 5A
- Wire Length: 25 feet (rear to auxiliary battery)
- Voltage Tolerance: Standard (5%)
- Load Type: Continuous
Results:
- Wire: 12 AWG (upgraded from 16 AWG for voltage drop)
- Fuse: 7.5A
- Explanation: Long run requires thicker wire
Shopping List:
- 55 feet of 12 AWG wire (buffer included)
- 7.5A blade fuse
- Fuse holder
- Anderson connector (recommended)
Scenario 3: Front-Mounted Winch
Inputs:
- Amp Draw: 200A (continuous rating)
- Wire Length: 8 feet (winch to battery)
- Voltage Tolerance: Conservative (3%)
- Load Type: Intermittent
Results:
- Wire: 2/0 AWG or 1/0 AWG
- Fuse: 200A or 225A ANL
- Warning: High current installation
Shopping List:
- 20 feet of 2/0 AWG welding cable
- 225A ANL fuse
- ANL fuse holder
- Heavy-duty lugs
Tips for Best Results
Tip #1: Measure Accurately
Use a tape measure or string to follow the actual wire path. Don’t guess - a few extra feet of wire run can make a difference in voltage drop.
Tip #2: Round Up Wire Length
Add 10% extra for connections, routing around obstacles, and future-proofing.
Tip #3: Document Everything
Screenshot your results or write down:
- Device name
- Wire gauge
- Fuse size
- Wire length used
Tip #4: Buy Quality Wire
Use marine-grade or automotive-grade stranded copper wire. Don’t use solid core or cheap wire from hardware stores.
Tip #5: Size Ground Wire Same as Power
Always use the same gauge for both power and ground wires. Voltage drop happens on both.
Tip #6: Test Before Finalizing
After installation, measure voltage at the device with a multimeter. It should be within 0.5V of battery voltage.
Troubleshooting
“Result seems too conservative”
- Try changing Voltage Tolerance to Standard (5%) or Relaxed (10%)
- Remember: conservative recommendations prevent problems
“Fuse size seems odd”
- Wire Solved uses standard fuse sizes
- Rounds up to nearest available size
- Includes 125% buffer for safety
“Wire gauge is huge for my small device”
- Long wire runs require thicker wire even for small loads
- Voltage drop is the issue, not amperage
- This is correct - don’t downsize
“Results different from online charts”
- Most charts ignore wire length
- Wire Solved factors in BOTH amperage and length
- Our results are more accurate
What’s Next?
Now that you know how to use the calculator:
- Wire Sizing 101 - Understand the theory
- Understanding Voltage Drop - Deep dive
- Fuse Sizing Guide - Protect your circuits