sorry, not trying to sound like a as$ hole, but honestly, there is no way to tell exactly how much you would need. Llike my bat neg to chassis was only 2inches.... and from my alt to bat pos was maybe 4ft etc, and engine block to chassis was maybe 6inches or so. So i didnt need much at all
But it really depends on your car and how you want to install it....because i could have easily had a longer run from my alt to battery positive, going back and up near the firewall and back down....instead of the route i took.