Oct 31, 2018· Red Brand barbed wire fence and Red Brand field fence are available in different roll lengths. If you're purchasing barbed wire, one roll is equal to 1,320 feet of fence, or 1/4 of a mile. Therefore, for a 40-acre square area that requires 1/4 mile of fencing on each side, you will need one mile of fencing, or four rolls of barbed wire per line.