When a serving of milk says it contains 30% calcium, how do I know how much calcium is in that serving?

Daily Values (DV) are standardized measures developed by the U.S.   Food and Drug Administration (FDA) to help people learn the amount of   specific nutrients contained in foods. The DV also allows you to compare   the nutrients in one food product to another.

The percent DV helps you determine whether a food is high or low in a   nutrient. In general, 5% DV or less is low in a nutrient, while 20% DV   or more is high. Daily Values are printed on the “Nutrition Facts” panel   on food labels. The percent DV is based on one serving of food. Be sure   to read the label carefully to learn the serving size and the number of   servings.

The DV for calcium is based on 1,000 mg. This means a serving of milk with a Daily Value of 30% calcium has 300 mg of calcium.

In the case of vitamin D, the DV is based on 400 IU for adults. This   means a food serving with a Daily Value of 25% vitamin D has 100 IU of   vitamin D. There are few food sources for vitamin D. So, unless an item   has been fortified with vitamin D, most food labels do not list the   percent of the DV of vitamin D.

NOF recommends that adults age 50 and older get 1,200 mg of calcium   every day, and adults under age 50 get 1,000 mg of calcium every day.   Often, a balanced diet can include up to 250 mg of calcium from trace   sources that are difficult to count, such as broccoli and certain green   vegetables.

Getting enough vitamin D every day is important to help your body   absorb calcium. Adults age 50 and older need 800-1,000 IU of vitamin D   every day, and adults under age 50 need 400-800 IU of vitamin D every   day. Older individuals and those with osteoporosis may need more.