Calculate net carbs in the UK vs USA | Deliciously Guilt Free (total carbs - polyols = net carbs) For the blueberry and lemon drizzle cake. 8.7-6.7 = 2g net carbs. On our labels we have worked this out for you- and you will see on most of the products at the top "effective carbs" or "net carbs"- it really means the same thing.