calculate percentage carbohydrate
How to Calculate the Carbohydrate Percentage. The total calories a food contains is listed near the top of the nutrition facts label, with grams of carbohydrate several lines underneath. To calculate the percentage of carbohydrate, take the grams of carbohydrate listed and multiply it by four.he total calories a food contains is listed near the top of the nutrition facts label, with grams of carbohydrate several lines underneath. To calculate the percentage of carbohydrate, take the grams of carbohydrate listed and multiply it by four.