Almonds and rice have even less calcium by nature. Each 8-ounce cup of plain almond milk contains a meager 2 milligrams of calcium, and less than 1 milligram is found in rice milk.Therefore, homemade or unfortified soy, almond and rice milk should not be used to replace cow's milk as a source of calcium.Fortification: Calcium and Vitamin D.ach 8-ounce cup of plain almond milk contains a meager 2 milligrams of calcium, and less than 1 milligram is found in rice milk. Therefore, homemade or unfortified soy, almond and rice milk should not be used to replace cow's milk as a source of calcium. Fortification: Calcium and Vitamin D.