First a calf determines how much mass it wants to eat, the Satiation Mass, SM, using the equations described below. Then, using the % of diet from milk curve, we calculate how much mass comes from milk. The remainder would have to be made up from food. For example, if a 60 day old whale wants to eat 15 kg, then 98% would come from milk or 14.7 kg from milk, and the remaining .3 kg it wants would have to come from prey.