12V Voltage Drop Calculator (Australia)
Work out voltage drop and end-voltage for your 12 V setup in seconds. This tool supports mm² and AWG, and is ideal for automotive, 4WD, caravan/RV and marine wiring in Australian conditions.
Quick tips: measure cable one-way length; the calculator will convert to round trip. For critical loads (fridges, compressors, DC-DC chargers) aim for ≤ 3% drop; ≤ 5% is typical for non-critical loads.
Voltage Drop Calculator
Assumes copper at 20 °C (ρ ≈ 0.0172 Ω·mm²/m). Total circuit length is out-and-back.
How to use
- Enter system voltage (usually 12 V), load current (A) and the one-way cable length (m).
- Select cable size in mm² or AWG.
- (Optional) Set a target drop (%) to see the minimum recommended cable size.
What affects voltage drop?
- Cable cross-section (mm²) – larger area = lower resistance.
- Run length – longer runs mean higher drop (out-and-back).
- Current draw – higher current increases drop.
- Connections & temperature – poor joints and heat increase resistance; size up for harsh WA/Outback conditions.
Need parts or install?
Shop cable, fuses, Anderson plugs & accessories online.
Guidance is general only. Always verify against manufacturer specifications and relevant Australian standards for your application.