The foods with the highest calcium content include dark, leafy green vegetables, dairy, sardines, fortified cereal and fruit juice, select seafood and some types of frozen foods. Some foods contain high amounts of calcium naturally, such as kale, spinach and collard greens, say experts at WebMD. Others derive an equally high amount of calcium through fortification, such as enriched cereal grains, bread and waffles.
Although many foods contain calcium, their levels per serving vary. In the category of greens, collard greens, broccoli rabe and kale take the lead with highest calcium content. Per each 8-ounce serving, these vegetables pack 360 milligrams, 200 milligrams and 180 milligrams of calcium, respectively, although the National Osteoporosis Foundation, which provides the calcium scale chart, states that the actual calcium level in these foods may vary. Leading the chart for seafood with the most calcium are canned sardines, salmon and shrimp. A three-ounce serving of each contains roughly 325 milligrams, 180 milligrams and 125 milligrams of calcium, respectively. A 4-ounce serving of ricotta packs the most calcium among dairy products, with around 335 milligrams, while a 6-ounce serving of plain, low-fat yogurt contains 310 milligrams and 8 ounces of non-fat skim milk contains 300 milligrams. Eight ounces of fortified milks and fruit juices contain 300 milligrams of calcium per serving while 4 ounces of enriched tofu packs 205 milligrams of calcium. Frozen macaroni, pizza and pudding contains up to 325, 115 and 160 milligrams of calcium.