Net carbs = total carbs − fiber (when using food labels)
If “fiber” is already listed as dietary fiber, subtract that amount directly
If “sugar alcohols” are listed, subtract usable sugar alcohols using product-specific rules
Common assumption: subtract sugar alcohols except those that are typically counted as fully net (varies by product)
If a label lists “total carbs,” “dietary fiber,” and “sugar alcohols,” use:
Net carbs = total carbs − dietary fiber − usable sugar alcohols
If fiber is not listed, do not estimate net carbs from other fields
If only “carbohydrates” and “fiber” are provided, use:
Net carbs = carbohydrates − fiber
For composite foods, sum net carbs from each ingredient and divide by servings as needed
For serving-size accuracy, calculate net carbs per serving using the label’s serving size
For USDA/ingredient databases, use the same approach:
Net carbs = total carbs − fiber − (usable sugar alcohols, if present)