Ronnie, I agree with Pete 1 gallon will not be enough. I used 1-1/2 gallons on my first boat and ended up buying an xtra quart to finish up. The width of glass depends on how cheap you can get it. I used 38" wide 6 oz. glass on my first boat and 50" wide 5.5 oz. on my second boat. I got the 5.5 50" for $2.99 from Hamilton Marine. http://WWW.Hamiltonmarine.com I don't think you will find it cheaper anywhere else. I bought 20 yards for an 18' boat and had plenty as long as I cut out diagonally. On the first boat I bought 27 yards of 38" and had a couple of yards left.