The percent daily value is a U.S. Food and Drug Administration sanctioned system to help Americans determine the amount of nutrients they should consume everyday. The system is based on a 2,000 calorie diet. The Nutrition Facts labels display the quantity of most major nutrients and the percent daily value of these nutrients. You can also calculate these values yourself by accessing the recommended amounts of each nutrient.
Reference the FDA recommended quantity of a given nutrient. As an example, the FDA recommends 50 grams of protein in a 2,000 calorie daily diet.
Read the label or other source to determine the amount of a given nutrient contained in some food. As an example, you might have a protein bar that offers 20 grams of protein.
Divide the amount of a nutrient in the food by the recommended amount; then multiply by 100 to convert to a percentage. In the example, 20 grams of protein in the protein bar, divided by 50 grams of recommended protein ingestion, results in a decimal value of 0.40. Multiply that by 100 to get the percent daily value of 40 percent.