I'm making some assumptions here that I'm not sure are absolutely accurate, but this is close enough for g-work.

Using about 8.3 lbs/gallon of water, a gallon of 6% sodium hypochlorite bleach should contain about 8 oz. of sodium hypochlorite. A pound of calcium hypochlorite at 65% should give you about 10.4 oz of the calcium hypochlorite. As someone else said, about 25% more active ingredient in the cal-hypo.