A creature's weight is determined by its SIZE. On average, it is equal to (3 + SIZE)³ lb. However, there is some variation from creature to creature. The actual weight could be anything from (3 + (SIZE - 0.5))³ lb. to (3 + (SIZE + 0.5))³ lb. Creatures with a size of 0.5 have an average weight of 15 lb. And those of size 0.25 have an average weight of 0.002 lb.