How to configure net carbs for low-carb and keto diets

November 17, 2025 •

4 min read

Did you know that the term "net carbs" isn't officially regulated by the FDA, leading to varying calculation methods depending on the source? Understanding how to configure net carbs accurately is a crucial skill for anyone following a low-carb, keto, or diabetic diet to manage carbohydrate intake effectively.

Quick Summary

Understand the key differences between total and net carbohydrates, and learn the precise formulas for calculating net carbs by properly accounting for dietary fiber and various sugar alcohols.

Key Points

Start with the Label: Always begin by checking the Total Carbohydrate and Dietary Fiber values on the nutrition label.
Handle Fiber Correctly: Subtract the entire amount of dietary fiber from the total carbs, as it is largely indigestible and doesn't impact blood sugar.
Be Cautious with Sugar Alcohols: The way you subtract sugar alcohols depends on the type. Some (like erythritol) can be fully subtracted, while others should only be partially accounted for.
Prioritize Whole Foods: Focus on foods naturally low in net carbs and high in fiber, like leafy greens, rather than relying heavily on processed 'low-carb' products.
Consult a Professional: The term 'net carbs' is not regulated, and individual responses can vary. For medical conditions or weight loss, a dietitian can offer personalized advice.
Remember Serving Size: Always adjust your calculation based on the actual serving size you consume, as label information is for a single portion.

Understanding Net Carbs vs. Total Carbs

For those managing their carbohydrate intake, especially on a ketogenic or low-carb diet, distinguishing between total and net carbs is fundamental. Total carbohydrates represent every gram of carbohydrate in a food, including sugars, starches, and fiber. Net carbs, on the other hand, are the carbohydrates that your body can actually digest and convert into glucose, thus impacting your blood sugar levels. The key to configuring net carbs lies in identifying and subtracting the carbohydrates your body cannot or only partially digests, such as fiber and certain sugar alcohols. This calculation provides a more accurate picture of a food's impact on your diet goals.

The Core Formula: Subtracting Fiber

The simplest and most universal step in calculating net carbs is subtracting dietary fiber. Fiber is a complex carbohydrate that your body cannot break down and absorb for energy. Instead, it passes through your digestive system largely unchanged, which means it doesn't raise your blood sugar. For this reason, all dietary fiber is subtracted from the total carbohydrate count. Here is the basic formula:

Net Carbs = Total Carbohydrates - Dietary Fiber

This method is particularly useful for whole, unprocessed foods like vegetables and fruits, where fiber is the only non-digestible carbohydrate present. For example, if a serving of avocado has 9g of total carbs and 7g of fiber, its net carb count is 2g (9g - 7g = 2g).

Handling Sugar Alcohols and Allulose

When dealing with processed low-carb foods, the calculation becomes more nuanced due to the presence of sugar alcohols (also known as polyols). These sweeteners are only partially digested and can have varying effects on blood sugar depending on the type. Here's how to incorporate them into your net carb calculation:

Fully Subtract Certain Sugar Alcohols: Some sugar alcohols, such as erythritol, mannitol, and allulose, have a minimal impact on blood sugar and can be completely subtracted from the total carb count.
Partially Subtract Other Sugar Alcohols: Slower-processing sugar alcohols like maltitol, sorbitol, xylitol, and isomalt can still affect blood sugar to some degree. For these, it is generally recommended to subtract only half of their total value.

Net Carbs (with sugar alcohols) = Total Carbohydrates - Dietary Fiber - (Specific Sugar Alcohols) - (Other Sugar Alcohols / 2)

How to Calculate Net Carbs Step-by-Step

To accurately configure net carbs, follow these steps when looking at a nutrition label, especially for packaged foods:

Check the Serving Size: Note the serving size and the number of servings you plan to consume. All nutritional information is based on a single serving.
Find Total Carbohydrates: Locate the "Total Carbohydrate" line on the nutrition label.
Identify Dietary Fiber: Find the "Dietary Fiber" line, which is indented under "Total Carbohydrate."
Look for Sugar Alcohols: Check if "Sugar Alcohols" or specific types like "Erythritol" are listed. If not listed, assume there are none.
Perform the Calculation: Apply the appropriate formula. Subtract the total dietary fiber. For sugar alcohols, subtract the full amount of those with minimal impact (erythritol, allulose) and half the amount of others (maltitol, sorbitol).

Comparison Table: Total Carbs vs. Net Carbs


Feature	Total Carbs	Net Carbs
Definition	All carbohydrates in a food, including fiber.	Digestible carbohydrates that impact blood sugar.
Includes	Starches, sugars, dietary fiber, and sugar alcohols.	Starches and sugars. Excludes fiber and specific sugar alcohols.
Impact on Blood Sugar	Varies widely based on carb type and fiber content.	Provides a more direct measure of a food's effect on blood sugar.
Best For	General dietary tracking and understanding macronutrient composition.	Low-carb diets (e.g., keto) where controlling blood sugar is the primary goal.
Regulatory Status	FDA-regulated and legally defined.	Not legally defined or regulated by the FDA.

Potential Pitfalls of Relying on Net Carbs

While helpful, the net carb concept is not without its issues:

Inaccurate Food Labels: Since the term is unregulated, some manufacturers may use misleading calculations to market products as 'low-carb'. Always verify the ingredients yourself.
Individual Sensitivities: Some individuals may have unique glycemic responses to certain sugar alcohols, even those generally considered non-impactful. Testing blood sugar levels after consumption is the only true way to know your body's reaction.
Overconsumption of Processed Foods: Focusing solely on the net carb number can sometimes lead to eating too many processed low-carb products, which may be low in nutrients and high in artificial ingredients.

The Best Way to Configure Net Carbs for Your Diet

For those on keto, keeping net carbs between 20-50 grams per day is a common guideline, though this can vary based on individual factors like activity level. For those managing diabetes, the American Diabetes Association recommends caution and suggests monitoring blood glucose levels, as the net carb calculation is not foolproof for all individuals. The best approach is to prioritize whole, fiber-rich foods like leafy greens, nuts, and berries, and to use the net carb calculation for informational purposes, particularly for processed foods.

Conclusion: Making the Right Choice for Your Health

Knowing how to configure net carbs empowers you to make more informed food choices, particularly on low-carb diets. By carefully reading nutrition labels and understanding the different effects of fiber and sugar alcohols, you can more accurately track your digestible carbohydrate intake. However, due to the lack of official regulation and individual variations, it's wise to complement this practice with mindful eating and prioritizing nutrient-dense, whole foods. When in doubt, or for those with specific health conditions like diabetes, consulting a registered dietitian is always the best strategy for personalized guidance. The ultimate goal is to find a sustainable and healthy approach that works best for your body, not just to follow a numerical formula. For more information on carbohydrate tracking, you can visit the American Diabetes Association's website to understand their recommendations regarding carbohydrate counting.

Frequently Asked Questions

The basic formula for calculating net carbs is: Total Carbohydrates minus Dietary Fiber. This applies primarily to unprocessed foods that do not contain sugar alcohols.

No, it depends on the type. You can fully subtract low-impact sugar alcohols like erythritol and allulose. For others, like maltitol and sorbitol, you should generally only subtract half of the amount because they can still affect blood sugar.

Keto dieters focus on net carbs because they are the carbohydrates that impact blood sugar and can potentially knock the body out of ketosis. Fiber and some sugar alcohols do not raise blood sugar significantly and are therefore not counted in the daily carb limit.

No, the term 'net carbs' is not legally defined or regulated by the U.S. Food and Drug Administration (FDA). For this reason, it's important to do your own calculation and not rely solely on package claims.

Examples of foods that are naturally low in net carbs include leafy greens (spinach, kale), broccoli, cauliflower, avocado, nuts, seeds, and most berries. These foods are also often high in beneficial fiber.

Yes, consuming too many sugar alcohols can cause digestive issues such as gas, bloating, and diarrhea, especially for individuals who are sensitive to them. It is best to consume them in moderation.

For individuals with diabetes, the American Diabetes Association recommends caution with net carb counting due to its unregulated nature and potential inaccuracies. It is often recommended to use total carbs for insulin dosing and to monitor blood sugar closely.