Grams of Carbs. Determine the number of grams of carbs you need each day by calculating 45 to 65 percent of your total calorie intake, and dividing by 4. For example, if you eat a 2,000-calorie diet, shoot for 225 to 325 grams of carbs per day; and if you eat 2,500 calories a day, aim for 281 to 406 grams of carbs.ercent of Calories. According to the Institute of Medicine, children and adults should consume 45 to 65 percent of their calorie intake as carbohydrates, and at least 130 grams of carbs per day.