As a standard, the Nutrition Facts label you see on the side of food packaging uses:
• 25 grams of dietary fiber for 2,000 calories per day, or
• 30 grams of dietary fiber for 2,500 calories per day
If you look at a label from 100% whole wheat bread, usually one slice has 3 grams of dietary fiber. One slice also has 12% Daily Value (%DV) for fiber. The 12% DV is arrived at by dividing the amount of fiber in one slice (3g) by the amount needed per day (25g). 3/25 = 12%.