Using the nutrition label take the number of carbs and subtract fiber and sugar alcohols. This will give you the net carbs per serving size. For example if something had 20 total carbs, 3g of fiber and 2g of sugar alcohol, it has 15 net carbs. Hope that answers your question.

From the nutritional information on the pack you can workout the total calories there are in carbohydrates. Most of the time... Gross energy input Carbohydrates (simple and complex) contain 4 calories/g Protein contain 4 calories/g Fat 9 calories/g Alcohol contain 7 calories/g non-starch polysaccharides" (NSP (Fibre)) 4 calories/g Fibre is considered a carbohydrate (complex) and carbs are 4 calories per gram. Since fibre is not completely digested in the body it is less than 4 calories per gram. As an estimate it is 1-2 calories per gram. This is where some confusion with packet labelling comes from when trying to work our calories. Net energy Input The 'Availability' to the body of ingested 'Macro-nutrients' determines the ultimate calories yield. Availability refers to completeness of digestion and absorption Normally about 97% for carbohydrates 95% for Lipids (fats) 92% protein become digested, absorbed and available for energy conversion. In other words if you consume 100g of carbohydrate 97 are avalable to the body and so on for other nutrients. Below is a web site that will give you a breakdown and I do mean a breakdown of all nutritional information in all common foods and some not normally mentioned + all fast food outlets http://www.nutritiondata.com/