Choose the right cable, according to AS3000. A Cross Sectional Area (CSA) of an AS3000 compliant conductor will cause a volt drop per meter per amp. You should have no more than 5% volt drop for full load current and no more than 10% volt drop for start up current - for a motor this is 5 times the full load current.
Example: You want to run a cable for a powerpoint in your shed 100m away. You may only pull 10A from a power point so that becomes the full load current. Lets say the biggest power tool you are going to run has a 1200W motor; divide that by 230(volts) gives you its full load requirement at 5.2A. Start up current for a motor is five times the full load current so the tool will draw 26A on startup. The calculator shows that although 4mm2 cable is fine for the full load current, only a 6mm2 cable meets the specification for start up current.
Note: Although we are dealing with 240VAC systems, AS3000 says we must do these calculations at a factor 1.04 which brings us down to 230VAC.