I found myself searching my way through the Apple iTunes store over the long Thanksgiving weekend and tripped over a really useful application for us boat wiring junkies. Simply titled Wire Sizer, this ap is a joy to use! Although only useful for DC wiring applications it does a great job. It has an initial set-up for measurement units and is basically a matter of entering the system operating voltage (up to 50 vdc), amount of amperage the circuit will be drawing, whether or not the wire run is going through an engine room space or not and what level of voltage drop you want to achieve. By simply scrolling through the on screen scales to set the specific values as shown in the video below you'll be able to get the right wire gauge to use every time. Nice.