Net Carbs Calculator
Total carbohydrate minus the part your body never digests.
Your food
How this is calculated
The formula: net carbs = total carbohydrate − dietary fiber − (sugar alcohols ÷ 2).
Why fiber comes out: human digestive enzymes cannot cleave fiber into glucose, so it contributes no blood-sugar load. It ferments in the colon instead, feeding the microbiome.
Why polyols are halved: erythritol is largely excreted unchanged, but maltitol and sorbitol are partly absorbed. Halving is the conservative middle ground.
Worked example: one cup of cooked black beans has 40.8 g total carbohydrate and 15 g fiber, so 40.8 − 15 = 25.8 g net carbs. A medium avocado has 17.1 g total and 13.5 g fiber — just 3.6 g net.
The plant-food pattern: intact plant foods carry their carbohydrate wrapped in fiber, so the gap between total and net is large. Refined foods lose that fiber, and total and net converge.
Frequently asked
How do you calculate net carbs?+
Net carbs = total carbohydrate − dietary fiber − half the sugar alcohols. Fiber is not absorbed as glucose, so it is subtracted in full. Sugar alcohols are partly metabolised, so the US convention subtracts 50% (erythritol is often subtracted entirely).
Why is fiber subtracted from carbs?+
Human enzymes cannot break down fiber into glucose. It passes to the colon where gut bacteria ferment part of it into short-chain fatty acids. Because it does not raise blood glucose the way starch and sugar do, low-carb frameworks exclude it from the usable carb count.
Do net carbs matter on a plant-based diet?+
They matter mostly for people managing blood glucose. Whole plant foods bundle carbohydrate with fiber, so their net carb figure is far lower than the label total — a cup of black beans is 40.8 g total but only 25.8 g net. That gap is the whole argument for eating carbohydrates in their intact form.
Are net carbs an official measurement?+
No. Neither the FDA nor EFSA regulates the term, and nutrition labels are not required to show it. It is an industry and diet-community convention, which is why manufacturers calculate it inconsistently. Compute it yourself from total carbs and fiber.
Should I subtract all sugar alcohols?+
Erythritol is almost entirely excreted unchanged and is usually subtracted in full. Maltitol, sorbitol, and xylitol are partly absorbed and do raise blood glucose, so subtracting half is the safer default this calculator uses.
Related tools & articles
References
- U.S. Food and Drug Administration. Food Labeling: Revision of the Nutrition and Supplement Facts Labels. Federal Register, 2016.
- National Academies of Sciences, Engineering, and Medicine. Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids. National Academies Press, 2005.
- U.S. Department of Agriculture, Agricultural Research Service. FoodData Central. USDA, 2024.
Educational estimates only, not medical advice. Individual needs vary — consult a physician or registered dietitian.