Calculate net carbs from total carbs, fiber, and sugar alcohols — the number that actually matters for staying in ketosis.
Calculate Net Carbs ↓Net Carbs = Total Carbs − Fiber − (Sugar Alcohols, per type below).
Dietary fiber passes through the digestive system largely intact — the body lacks the enzymes to break most of it down into glucose. Since it doesn't raise blood sugar or contribute usable energy the way other carbs do, most low-carb and keto tracking methods subtract it from the total carb count.
Sugar alcohols (erythritol, xylitol, maltitol, sorbitol) are sweeteners that are only partially absorbed and metabolised. Erythritol is absorbed into the bloodstream but excreted largely unchanged in urine without being metabolised, so it's typically subtracted at 100%. Others like maltitol are absorbed more completely and have a bigger effect on blood sugar, so trackers typically subtract only 50% of their grams.
Unlike 'total carbohydrates', which is a regulated label term in most countries, 'net carbs' has no standardised legal definition. This is why different apps, brands, and keto influencers sometimes calculate it slightly differently — the calculation logic here (fiber subtracted fully, sugar alcohols per type) reflects the most common convention, but always check labels carefully on packaged 'keto' products, since marketing claims aren't always consistent with the actual math.
Net carbs is a useful mental shortcut for keto and low-carb tracking, but it's a simplification. Individual responses to fiber and sugar alcohols vary — some people experience real blood sugar rises or digestive discomfort (bloating, gas) from sugar alcohols even when the label math says they 'don't count'. Highly processed 'net carb' snack products with lots of sugar alcohols can also be misleading: the total ingredient load may still affect some people's ketosis or digestion more than the printed net carb number suggests.
If you're using net carbs to manage a medical condition like diabetes, talk to your doctor or dietitian about which counting method they want you to use — carb counting for insulin dosing typically uses total carbs, not net carbs, unless specifically advised otherwise. This calculator is an educational tool for general keto/low-carb tracking, not medical dosing guidance.
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