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A 1200W inverter on a 12V system draws 100 Amps ( 1200 / 12 = 100 ).

Do not just measure the distance from the battery to the fridge. Electricity must travel from the battery to the fridge .

While online calculators are handy, understanding the math helps you verify their results. The formula used in Australia (metric) is: 12v cable size calculator australia

Example: 15A × 6m × 0.074 = 6.66 → 10 mm²

Recommended free tool: (Australian, includes AS/NZS derating). A 1200W inverter on a 12V system draws

Where:

(where metres = one‑way distance)

Current (Amps) = Power (Watts) / Voltage (Volts)

In the 12V world, voltage drop is the enemy. Unlike your household 240V circuits, where small voltage drops are negligible, a 0.5V drop in a 12V system represents a massive 4% loss of power. This results in dim lights, slow fridges, and overheating wires. While online calculators are handy, understanding the math

12v Cable Size Calculator Australia (Proven Method)

A 1200W inverter on a 12V system draws 100 Amps ( 1200 / 12 = 100 ).

Do not just measure the distance from the battery to the fridge. Electricity must travel from the battery to the fridge .

While online calculators are handy, understanding the math helps you verify their results. The formula used in Australia (metric) is:

Example: 15A × 6m × 0.074 = 6.66 → 10 mm²

Recommended free tool: (Australian, includes AS/NZS derating).

Where:

(where metres = one‑way distance)

Current (Amps) = Power (Watts) / Voltage (Volts)

In the 12V world, voltage drop is the enemy. Unlike your household 240V circuits, where small voltage drops are negligible, a 0.5V drop in a 12V system represents a massive 4% loss of power. This results in dim lights, slow fridges, and overheating wires.