Originally Posted by
adamrice
A fluid ounce is a unit of volume, not weight. One fluid ounce of water does not weigh exactly one ounce (thanks, Imperial system). A gallon displaces 128 fluid ounces, but a gallon of water weighs 133 oz.
There are 16 ounces in a pound. 100 ounces/(16 oz/lb) = 6.25 lb
My math was incorrect as I accidentally based it on 64 ounces being a gallon. Dumb mistake, too early in the morning. I stand corrected.