Net Carbs
- Net carbs = total carbohydrate − fiber − sugar alcohols — the carbs that meaningfully raise blood glucose. It is not an official, FDA-regulated term.
- US and EU labels differ: a US "Total Carbohydrate" includes fiber (subtract it); an EU "carbohydrate" figure already excludes fibre by definition (do not subtract it again).
- Sugar alcohols are not equal: erythritol is about 0 kcal/g; maltitol about 2.1 kcal/g. There is no official per-gram subtraction rule.
- Allulose breaks the standard formula — it sits inside Total Carbohydrate but is neither fiber nor a sugar alcohol, so "total − fiber − sugar alcohols" overstates its net carbs.
Net carbs are the carbohydrates that meaningfully raise blood glucose — calculated as total carbohydrate minus fiber and (typically) sugar alcohols. The term is a practical tracking tool used mainly on low-carb and keto diets. Importantly, "net carbs" is not a regulated or officially defined nutrition term, so its exact calculation varies.
The idea behind net carbs is that not every gram of carbohydrate affects the body the same way. Fiber and some sugar alcohols pass through largely undigested, or are absorbed without meaningfully raising blood sugar, so subtracting them estimates the carbohydrate that actually drives a glucose and insulin response. This is why keto and other low-carb approaches track net carbs rather than total carbohydrate. Because the term is unofficial, different labels, brands, and apps calculate it slightly differently — so it helps to understand the calculation yourself. For general carbohydrate targets, see our carb calculator guide.
Net Carb Calculator
Enter the numbers from a nutrition label. Choose US label or EU / UK label — the two are calculated differently (explained below), and getting the mode right matters.
On US labels, Total Carbohydrate already contains fiber and any declared sugar alcohols (21 CFR 101.9(c)(6)), so those are subtracted here.
This tool is for general education, not medical advice. It reflects the common net-carb convention, which is not an official standard.
Net Carbs vs Total Carbs
Total carbs is every gram of carbohydrate in a food — sugars, starches, and fiber together. Net carbs is the subset of that total which your body actually digests into glucose, after removing the parts that have little blood-sugar impact. In practice that means subtracting fiber, and usually sugar alcohols, from the total.
Which one should you track? For most people, total carbs is simpler and works fine — you do not need net carbs to eat well. Net carbs earn their keep on ketogenic and other low-carb plans, where the goal is to cap the carbohydrate that drives blood sugar and insulin. The catch is that "total carbs" itself is defined differently in the US and the EU, which is where most net-carb mistakes begin.
How to Calculate Net Carbs (US vs EU)
The calculation depends on how your label reports carbohydrate — and this is the step most guides get wrong.
In the United States, the Nutrition Facts label lists Total Carbohydrate, which the FDA calculates by difference — total food weight minus protein, fat, moisture, and ash (21 CFR 101.9(c)(6)). Because of that, the Total Carbohydrate figure includes dietary fiber, sugars, and any declared sugar alcohols, with fiber listed as a subcomponent beneath it. So you subtract them yourself:
Net carbs (US) = Total Carbohydrate − Fiber − Sugar Alcohols
In the European Union — and in regions that follow similar labelling conventions, such as the UK and Australia/New Zealand — the label's "carbohydrate" figure means available carbohydrate and already excludes fibre by definition. EU law defines carbohydrate as "any carbohydrate which is metabolised by humans, and includes polyols," while fibre is defined separately as carbohydrate that is "neither digested nor absorbed in the human small intestine" (Reg (EU) No 1169/2011, Annex I). Because fibre falls under that separate definition — carbohydrate not digested or absorbed in the small intestine — it is reported outside the "carbohydrate" figure entirely: a definitional exclusion, not a subtraction. So on an EU-style label:
Net carbs (EU-style label) ≈ carbohydrate − polyols
The printed carbohydrate figure still includes polyols (the EU definition says so explicitly), which is why you subtract those but not fibre — subtracting fibre again would double-count it. This is a labelling convention, not a physiological difference: fibre behaves the same in the body everywhere. It is also why the same food can show a different "net carb" number depending on which country's label you read.
Fiber: Why It's Subtracted
Fiber is carbohydrate that the human gut cannot fully digest, so it contributes little directly to blood glucose — which is the rationale for subtracting it (on US-style labels) or excluding it from the carbohydrate figure (on EU-style labels). Fiber comes in two broad types: soluble fiber, which dissolves in water and can slow digestion and blunt glucose spikes, and insoluble fiber, which adds bulk and largely passes through.
The honest caveat: "subtract all fiber" is an approximation. Some fibers are partially fermented by gut bacteria into short-chain fatty acids, which provide a small amount of energy — and regulators account for this. The EU explicitly assigns fibre an energy value of 2 kcal/g (Reg (EU) No 1169/2011, Annex XIV), a formal acknowledgement that fibre is not entirely calorie-free. Certain isolated or synthetic fibers added to processed "low-carb" products can also behave differently from the fiber naturally in whole foods. So the fiber you subtract is not always entirely "free."
Sugar Alcohols (Polyols)
Sugar alcohols — erythritol, maltitol, xylitol, sorbitol, and others — are often subtracted from carbs, but they are not all equal, and this is where blanket rules break down. Erythritol is absorbed and then excreted largely unchanged, so it has little effect on blood glucose and is commonly subtracted in full. Maltitol, by contrast, meaningfully raises blood sugar, so subtracting it completely overstates the reduction; sorbitol and xylitol fall somewhere in between. Because polyols differ so much, there is no standardized, official amount to subtract — practical trackers use rules of thumb, but these are approximations, not precise measures. For a practical, sweetener-by-sweetener breakdown aimed at keto, see our keto macro calculator guide.
The calorie content of polyols, however, is set by regulation — and it reveals the same point in hard numbers. The FDA assigns each polyol a specific caloric value per gram (21 CFR 101.9(c)(1)(i)(F)), while the EU applies a single flat 2.4 kcal/g to every polyol except erythritol (Reg (EU) No 1169/2011, Annex XIV). Same sweetener, a different legal calorie value depending on the jurisdiction — though both agree erythritol is 0 kcal/g.
Read the chart as calories, not glycemic impact: it shows energy per gram, which is a separate question from how much a polyol raises blood sugar. But it still makes the case against a blanket "subtract every gram of sugar alcohol" rule — erythritol at essentially 0 kcal/g is a safe full subtraction, while maltitol at 2.1 kcal/g is more than half of carbohydrate's 4 kcal/g, so treating it as "free" clearly overstates the reduction. (HSH is hydrogenated starch hydrolysates.)
Allulose: The Exception That Breaks the Formula
Allulose is a newer low-calorie sweetener that quietly breaks the standard net-carb math. It is a monosaccharide (D-psicose), not a sugar alcohol and not counted as a sugar. Under FDA guidance, allulose may be excluded from Total Sugars and Added Sugars, must still be included in Total Carbohydrate, and may be counted at about 0.4 kcal/g (FDA Guidance for Industry, 2020).
Here is the problem: the popular formula "total carbohydrate − fiber − sugar alcohols" does not remove allulose, because allulose is neither fiber nor a sugar alcohol. So for a product sweetened with allulose, that formula overstates net carbs — it leaves allulose in, even though allulose contributes little glucose and only about 0.4 kcal/g. This is exactly why the calculator above has a separate optional allulose field: it lets you subtract what the standard formula would miss.
Why "Zero Net Carb" Claims Can Mislead
"Zero net carb" and "low net carb" claims are marketing, not regulated statements — and because net carbs is an unofficial term, the number behind the claim can be reached in ways that flatter the product. A few things to check for yourself, without needing to trust the front-of-pack math:
- Maltitol counted as if it were free. If the sugar alcohol is maltitol (common in "sugar-free" candy and some bars), subtracting all of it treats a carbohydrate that does raise blood sugar as if it does not.
- Added, isolated fibers. Some products lean on isolated fibers (such as soluble corn fiber or IMO syrups) that can behave differently in the body from the fiber in whole foods, so "subtract all fiber" may not fully hold.
- Allulose accounting. As above — allulose is genuinely low-impact, but how it is presented on the label varies, so a "0 net carb" figure may depend on subtractions the standard formula does not make.
- Check the label yourself. Read Total Carbohydrate, fiber, sugar alcohols, and (if listed) allulose, then do the arithmetic — and remember maltitol is the usual reason a real-world number lands higher than the claim.
None of this means low-net-carb products are bad; many are genuinely useful. The point is that the claim is only as good as the assumptions behind it, and you can check those assumptions in about ten seconds with the label.
Net Carbs in Common Foods
These values come from the USDA's reference database (net carbs = carbohydrate by difference − total dietary fiber). Whole plant foods are shown raw unless noted; the exact USDA record for each is linked by its FoodData Central (FDC) ID.
| Food | FDC ID | Total carb /100g | Fiber /100g | Net carbs /100g | Per common serving |
|---|---|---|---|---|---|
| Avocado | 171705 | 8.53 g | 6.7 g | 1.83 g | ½ avocado (~100 g) → 1.8 g |
| Spinach | 168462 | 3.63 g | 2.2 g | 1.43 g | 1 cup (30 g) → 0.4 g |
| Cauliflower | 169986 | 4.97 g | 2.0 g | 2.97 g | 1 cup chopped (107 g) → 3.2 g |
| Broccoli | 170379 | 6.64 g | 2.6 g | 4.04 g | 1 cup chopped (91 g) → 3.7 g |
| Blackberries | 173946 | 9.61 g | 5.3 g | 4.31 g | 1 cup (144 g) → 6.2 g |
| Brussels sprouts | 170383 | 8.95 g | 3.8 g | 5.15 g | 1 cup (88 g) → 4.5 g |
| Raspberries | 167755 | 11.94 g | 6.5 g | 5.44 g | 1 cup (123 g) → 6.7 g |
| Chia seeds | 170554 | 42.12 g | 34.4 g | 7.72 g | 1 oz, ~2 tbsp (28 g) → 2.2 g |
| Almonds | 170567 | 21.55 g | 12.5 g | 9.05 g | 1 oz, 23 kernels (28 g) → 2.6 g |
| Sweet potato (baked) | 168483 | 20.71 g | 3.3 g | 17.41 g | 1 medium (114 g) → 19.8 g |
Source: U.S. Department of Agriculture, Agricultural Research Service. FoodData Central, SR Legacy. Sweet potato is shown baked; cooking changes per-100 g values through water loss, so raw and cooked figures differ. USDA values are population means with real sample variation — treat them as representative, not exact.
Who Net Carbs Are For — and the Limit
Net carbs are most useful for people on ketogenic or other low-carb diets, where the goal is to limit the carbohydrate that drives blood sugar and insulin in order to reach or maintain ketosis. For most other people, simply tracking total carbohydrate is easier and works just as well — see our carb calculator guide, or set your overall targets with the free macro calculator.
The limitation to keep in mind: net carbs are a practical heuristic, not a precise physiological measurement. Individual blood-sugar responses to the same food vary, sugar alcohols differ from one another, allulose and some added fibers sit outside the standard formula, and fiber fermentation is not uniform. Net carbs are a useful estimate for planning a low-carb diet — not an exact account of how a food will affect any one person.
Frequently Asked Questions
What are net carbs?
Net carbs are the carbohydrates that meaningfully raise blood glucose — total carbohydrate minus fiber and (typically) sugar alcohols. It is a practical tracking tool used mainly on keto and low-carb diets, and it is not an officially regulated nutrition term.
What does net carbs mean?
"Net carbs" means the portion of a food's carbohydrate that your body digests into glucose. It removes components that have little blood-sugar impact — mainly fiber, and often sugar alcohols — from the total carbohydrate, leaving the carbs that actually count for a low-carb or keto plan.
What's the difference between net carbs and total carbs?
Total carbs is every gram of carbohydrate in a food, including fiber. Net carbs subtract the parts that have little effect on blood sugar (fiber, and usually sugar alcohols). On a US label, fiber is already inside Total Carbohydrate, so you subtract it; on an EU label, the carbohydrate figure already excludes fibre.
How do you calculate net carbs?
On a US label, net carbs = Total Carbohydrate − fiber − sugar alcohols. On an EU/UK label the "carbohydrate" figure already excludes fibre, so net carbs ≈ carbohydrate − polyols; subtracting fibre again would double-count it.
Do you subtract sugar alcohols?
Some, but not all. Erythritol has almost no effect on blood sugar and about 0 kcal/g, so it is usually subtracted fully. Maltitol meaningfully raises glucose and carries about 2.1 kcal/g, so subtracting it in full overstates the reduction. There is no official per-gram subtraction rule.
Is net carbs an official FDA term?
No. "Net carbs" is not defined or regulated by the FDA. US labels must show Total Carbohydrate and Dietary Fiber (21 CFR 101.9), but net carbs is an unofficial calculation, which is why brands and apps compute it differently.
References
- U.S. Food and Drug Administration. 21 CFR 101.9 — Nutrition labeling of food. Total Carbohydrate calculated by difference with dietary fiber declared beneath it, §(c)(6); caloric values for sugar alcohols, §(c)(1)(i)(F). Electronic Code of Federal Regulations. ecfr.gov
- European Union. Regulation (EU) No 1169/2011 on the provision of food information to consumers. Annex I (definitions: "carbohydrate" includes polyols; "fibre" is not digested or absorbed in the small intestine); Annex XIV (energy conversion factors: polyols 2.4 kcal/g, fibre 2 kcal/g, erythritol 0 kcal/g). EUR-Lex. eur-lex.europa.eu
- U.S. Food and Drug Administration. Guidance for Industry: The Declaration of Allulose and Calories from Allulose on Nutrition and Supplement Facts Labels (final, October 2020; Docket FDA-2019-D-0725). fda.gov
This page is for general education and is not medical advice; individual needs vary.