Hi Dan.

If you need 1,270,500 linear feet of strip and you are making 6 strips per roll, then you need 1,270,500/6 = 211,750 linear feet of stock.

The area of the annulus (the ring) of stock around the core will determine how much stock you have. This is simply the area of a 20" diameter circle minus the area of a 4" diameter circle. That's 10² π - 2² π = 298.45 square inches.

If we unroll the stock, this area would be the same as a rectangle that is 0.008" thick by the linear inches on the roll. Divide that by 12 to get linear feet.

So there is ( (298.45 / 0.008 ) / 12) = 3108.87 linear feet of stock on each roll.

Since we need 211,750 linear feet of roll, we just divide 211,750 / 3108.87 and get 68.1 rolls.

Cheers,
Stephen La Rocque.