Cable Sizing & Voltage Drop Calculator

A simple tool to help you choose the correct cable size for 12/24V campervan circuits. Select what you’re powering, enter the system voltage and cable length, and we’ll estimate the minimum cable size needed.

This tool estimates voltage drop using copper cable at ~20 °C. We use about 3% max voltage drop for most leisure circuits (lighting/electronics), and about 5% for motor loads (pumps/fans), which typically tolerate more drop. For high-current circuits (especially inverters), cable must also be sized for heat/current capacity and surge current — always follow the manufacturer’s guidance and consult a qualified auto electrician if unsure.