Speaker wire length?

I'm not an audio nut, but I can get some by-the-foot aftermarket wire for cheap and it should be a good way for me to improve the sound of my stereo. So does anyone know off hand what the total length of speaker that wire runs through the cabin of a hatchback? Or how many feet are needed to do the job? Also should I get 16 ga wire, its just for a middle of the road Pioneer unit (circa 2004).

I'm only considering doing it because I can buy nice by-the-foot wire like the spiral type for well under a buck from my job. Also the stock speaker wiring in my drivers door is shorted out, so when I close the door the speaker doesnt work, open the door and theres sound, so I have a reason to do it. Right now I have it bypassed with some cheapo wire; maybe I'll just see what $20 worth or wire will get me.