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How to Calculate the Percent of RDA

Updated April 17, 2017

Look at the packaging for just about any food and you will see a "Nutrition Facts" box. The box tells you some basic information about the nutritional value of the food and how it contributes toward your RDA, or recommended daily allowance. The U.S. Food and Drug Administration sets the RDA for certain vitamins, minerals and fats based on a healthy 2,000-calorie diet. Stay below the RDA for fats and sodium, and meet or exceed the RDA for vitamins and other minerals to stay healthy, according to the FDA. Learn how to calculate the per cent of RDA to better understand what makes a healthy diet.

Navigate to FDA.gov. In the search box at the top-right of the page, enter the phrase "Calculate the Percent Daily Value for the Appropriate Nutrients" and press "Enter."

Select the result that begins, "Appendix F." This is the chart food manufacturers use to compute daily values, based on an average person. Read the chart to find the total RDA of the nutrient for which you want to calculate a per cent of RDA. As an example, note that the average person should consume 60 milligrams of vitamin C in a day.

Divide by the RDA in the chart the amount of the nutrient that is in the food for which you want to calculate the per cent of RDA. For example, if it had 20 milligrams of vitamin C, divide 20 by 60 to get 0.33.

Multiply the answer by 10 to find the percentage of the RDA. In the example you would see that the food contains 33 per cent of the recommended daily allowance of vitamin C.

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About the Author

James McElroy began his journalism career in 2001 and his stories have appeared in newspapers around the world, including "The Columbus Dispatch" and "The Star-Ledger." He studied journalism at the E.W. Scripps Graduate School of Journalism at Ohio University in Athens, Ohio.