I would like to know how to calculate the cable size needed for 300W,12V bulb. The distance for the location is 50meter length. Any others info I need to put here? Could anyone send me the formula so that I can calculate it?

Thanks

Mike:)

Here is the Ohm's Law Pie Chart, it should have everything you need, with exception of voltage drop.

Do a search for Voltage Drop Online calculator, and you will find several.