What Are Net Carbs?

“Net carbs” is total carbohydrate minus the carbohydrate your body doesn’t fully digest: always the fiber, and often some or all of the sugar alcohols too. The idea is to count only the carbohydrate that raises blood sugar and supplies full energy. It’s popular with low-carbohydrate and ketogenic diets, but it isn’t a regulated term: neither the US nor the EU labelling rules define it, so each brand and app can count it its own way.

This article is general information, not medical advice. If you manage diabetes, count carbohydrate the way your care team advises.

The Arithmetic

net carbs = total carbohydrate − fiber (− some or all sugar alcohols)

A food with 20 g of total carbohydrate, 8 g of fiber, and 6 g of erythritol is 12 g of net carbs counting only fiber, or 6 g subtracting the erythritol as well. Some products subtract every sugar alcohol in full, others only some of them. The result depends on the rule, so two numbers called net carbs aren’t necessarily comparable.

What Labels Say

• United States. On the Nutrition Facts label, total carbohydrate is calculated by difference: the food’s weight minus its protein, fat, moisture, and ash. So it includes fiber, sugars, and sugar alcohols. Sugar alcohols are a voluntary line, required only when a claim is made about them or about sugars. “Net carbs” appears nowhere in the rule (21 CFR 101.9).
• European Union. Under Regulation 1169/2011, carbohydrate is carbohydrate metabolised by humans, including polyols (sugar alcohols), and fibre is listed separately as carbohydrate neither digested nor absorbed in the small intestine. So a European label’s carbohydrate already leaves fiber out, and is close to a net figure that counts fiber only.

That difference matters when you compare: 20 g of carbohydrate on a US label and 20 g on a European label can be different amounts of the same food.

Fiber and Sugar Alcohols Still Have Energy

Subtracting them doesn’t make them free:

• Fiber is fermented in the large intestine and yields some energy; EU labelling counts it at 2 kcal per gram, against 4 for other carbohydrate.
• Sugar alcohols are partly absorbed. The FDA’s factors range from 0 kcal per gram for erythritol to 1.6 for mannitol, 2.4 for xylitol, 2.6 for sorbitol, and 3.0 for hydrogenated starch hydrolysates; EU labels use 2.4 kcal per gram for every polyol except erythritol, at 0.
• Large amounts of sugar alcohols can cause bloating and diarrhoea; EU labels must warn of laxative effects when a food contains more than 10% added polyols.

The health effects of sugar alcohols are still being studied. In 2023, Witkowski and colleagues found that people with higher blood levels of erythritol had a higher risk of death, heart attack, or stroke over three years. That’s an association in people undergoing heart checks, which doesn’t show erythritol causes them, but it’s a reason not to treat sweeteners as free.

Following It in Kaizora

Dietary Total Carbohydrate and Dietary Fiber are on the Food Log from foods logged from the Food Database (with the USDA’s FoodData Central values, where total carbohydrate is by difference, as on a US label), from Cronometer imports, and from Apple Health. Dietary Net Carbohydrate is kept as your source counts it, never computed: it comes from Cronometer’s Net Carbs column, or from a custom food you add with its own net carbs. FoodData Central has no net carbohydrate, so catalog foods leave it empty. Dietary Sugar Alcohols come only from custom foods you enter them on. Because sources count it differently, compare net carbs only within one source.

Fiber has default reference ranges from the Dietary Reference Intakes’ Adequate Intakes, judged over the 7 days ending each day. See How to Track Your Protein and Fiber Over Weeks, Not Days and Add a Custom Food.

The Short Version

• Net carbs are total carbohydrate minus fiber, and sometimes minus sugar alcohols.
• No US or EU rule defines them, so brands and apps count them differently.
• A US label’s total carbohydrate includes fiber; a European label’s carbohydrate doesn’t.
• Fiber and most sugar alcohols still provide some energy.

Sources

• US Code of Federal Regulations, 21 CFR 101.9, Nutrition labeling of food.
• European Union, Regulation (EU) No 1169/2011 on the provision of food information to consumers, Annexes I, III, and XIV.
• Witkowski M et al., “The artificial sweetener erythritol and cardiovascular event risk,” Nature Medicine 29, no. 3 (2023): 710–718. doi:10.1038/s41591-023-02223-9