Cable Size (Gauge) Calculator
Minimum DC cable size for current and run length.
About the Cable size calculator
Use this cable size (gauge) calculator for van leisure battery & solar setup. Minimum DC cable size for current and run length.
Enter your cable size details
From battery to device — we double it for round-trip.
3% is the usual target for critical runs.
Why bigger is fine
Going one size up costs little, runs cooler and gives margin. Undersized DC cable wastes power as heat and can cause fires.
Your cable size results
Allowed drop
0.36 V
3% of 12 V
Min copper
11.67 mm²
3 m run, 40 A
Use cable
16 mm²
6 AWG
Why cable size matters for van leisure battery & solar setup
Plan with confidence
Getting your cable size numbers right early avoids costly rework, undersized components and surprises on the road.
Related battery & solar tools
Pair this with the rest of our battery & solar calculators to plan your full van conversion.
Cable size calculator FAQ
- What does the Cable Size (Gauge) Calculator do?
- Minimum DC cable size for current and run length. It is designed for van leisure battery and solar so you can plan with confidence.
- Is the cable size calculator free to use?
- Yes. All VanTools calculators, including the Cable Size (Gauge) Calculator, are free to use with no sign-up required.
- How accurate are the cable size results?
- Results are estimates based on the values you enter and standard van leisure battery and solar assumptions. Always sanity-check against manufacturer data and your real-world conditions.
- Can I share or save my cable size calculation?
- Yes. Use the Share button to copy a link that includes your inputs, or use Export to download a PDF or image of your results.