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.rinking three cups of milk per day can effectively keep you safe from calcium deficiency. The naturally occurring calcium in soy is only about 1/6 of the amount found in dairy. Therefore, homemade soy milk contains only about 50 milligrams of calcium in each 8-ounce serving.