Electrical cable section calculation – Camper, solar, boat, house
How to calculate the correct electrical cable section for your solar, 12V or 230V installation?
Are you installing a solar panel, a voltage converter, a battery, a wind turbine, or LED lighting in a camper, boat, garden shed, or an off-grid system? Great initiative, but a crucial question arises: which electrical cable section to choose?
Why properly size the cable sections?
At 12 volts or 24 volts, losses are much greater than at 230 volts. Contrary to what one might think, the lower the voltage, the thicker the cables need to be. An improperly sized cable acts like a resistor:
- Voltage drop (and thus reduced performance of solar panels, regulators, batteries...)
- Cable heating, oxidation, energy waste in heat
- Fire risk
- Poor operation or failure of electrical devices
- Measurement errors on solar regulators
- Increased energy consumption
What our cable section calculator does
Our calculator helps you automatically calculate the necessary cable section, without using complicated charts. It is useful for installations:
- in 12V / 24V (camper, boat, solar, wind turbine)
- in 48V or 230V (domestic or industrial applications)
- in direct or alternating current (single-phase or three-phase)
It works just as well for mobile use as for fixed installations.
Parameters to enter in the calculator
🔌 Voltage in volts
Value to indicate: 12V, 24V, 48V, 230V... A battery always provides direct current (DC).
📏 Total cable length
You must indicate the round-trip distance between the battery and the device. For example, if the panel is 5 m from the battery, enter 10 m.
⚡ Device power
Indicated in watts (W) on the device. If in doubt between several values, take the highest one.
🧮 Allowable voltage drop
- 3% by default (i.e., 0.36V for 12V)
- 0.2V recommended for sensitive equipment (solar regulator, charger...)
🧲 Cable resistivity
- Copper: 0.017 ohm·m (default value)
- Aluminum: 0.028
- Silver: 0.016
Results provided by the calculator
✅ Current (in amperes): calculated automatically
✅ Voltage drop (in volts and %)
✅ Power loss (thermal dissipation in watts)
✅ Cable temperature (estimated rise)
✅ Minimum cross-section (in mm², nearest standardized value)
The available standardized sections are:
0.75 – 1 – 1.5 – 2.5 – 4 – 6 – 10 – 16 – 25 mm²
Concrete examples of use
- 💡 12V / 10W LED lamp located 3 m from the battery → recommended cable: 1.5 mm²
- ⚡ 300W inverter with 4 m round-trip in 12V → minimum cross-section: 6 mm²
- ☀️ 100W solar panel on van → 2.5 mm² cable between regulator and battery
Fields of application
Our tool is ideal for:
- 🚐 Camper van, converted van, van life
- ⛵ Boating, boat, sailboat, barge
- 🏕️ Remote site (cabin, refuge, sheepfold)
- 🏠 House or domestic installation for self-consumption
- 🚲 Electric bike, solar trailer
- 🔋 Hybrid solar + wind installation
Advice for a secure installation
- Always slightly oversize the section to anticipate losses
- Add an appropriate fuse on each protected line
- Never exceed the current limits of the cables
- Favor copper, and well-insulated sheaths
- Check the fixings and cable passages (friction, humidity…)
Gain in performance and safety
The right cable choice will prevent:
- breakdowns
- energy losses
- risks of overheating or fire
Our tool is here to guide you simply, quickly, and for free.
🔢 Calculate your cable section now
It's time to move on to practice. Use our calculator below to obtain the ideal electrical cable section according to:
- the voltage of your installation (e.g., 12.5V),
- the power of your device (e.g., 100W),
- the total length of the cable round trip (e.g., 20 meters),
- the voltage drop you accept (e.g., 0.4V),
- and the type of current used (DC, single-phase, or three-phase).
💡 The calculator automatically provides you with:
- the theoretical section in mm²,
- the nearest standardized section,
- and the section in AWG (useful for automotive or onboard wiring).