What Gets Subtracted From Carbs? Your Guide to Calculating Net Carbs

December 29, 2025 •

4 min read

Your body processes carbohydrates in many different ways, with some forms being digested for energy while others pass through largely untouched. This crucial distinction is the basis for calculating "net carbs" and is particularly important for individuals managing their blood sugar or following specific low-carb diets.

Quick Summary

Net carbs are calculated by subtracting indigestible carbohydrates, such as dietary fiber and certain sugar alcohols, from a food's total carbohydrate count to determine its impact on blood sugar levels.

Key Points

Net Carbs vs. Total Carbs: Net carbs are calculated by subtracting non-digestible carbohydrates like fiber and sugar alcohols from the total carbs listed on a food label.
Dietary Fiber's Role: Fiber is a type of carbohydrate that the body cannot digest, so it does not raise blood glucose levels and is fully subtracted from total carbs.
Sugar Alcohol Considerations: Sugar alcohols are sweeteners with a minimal impact on blood sugar, but their effect varies by type. Erythritol is largely unabsorbed, while others like maltitol require subtracting only half.
Not Officially Regulated: The term "net carbs" is not recognized or regulated by the FDA, meaning packaged food claims should be verified by checking the nutrition facts yourself.
Relevant for Specific Diets: Tracking net carbs is most relevant for those on keto or other low-carb diets who need to monitor their glycemic load closely.
Importance of Whole Foods: For general health, focusing on a diet rich in whole foods naturally high in fiber is more beneficial than relying on net carb calculations for processed items.

Total Carbs vs. Net Carbs: The Foundational Difference

On any nutrition label in the United States, you will find a line for "Total Carbohydrates." This number represents the total amount of all types of carbohydrates in a single serving of a food product. This includes everything from simple sugars that cause a rapid blood glucose spike to complex carbohydrates and indigestible components like fiber.

Net carbs, on the other hand, are an informal metric used to measure only the carbohydrates that your body can fully digest and use for energy. The key premise is that not all carbohydrates raise your blood sugar in the same way. By subtracting carbohydrates that have little to no glycemic impact, you arrive at a more relevant number for specific dietary strategies, such as a ketogenic diet.

The Components You Subtract

The Indigestible Role of Dietary Fiber

Dietary fiber is a type of carbohydrate that your body lacks the enzymes to break down and absorb. As a result, it passes through your digestive system largely intact. This is the primary reason it is subtracted when calculating net carbs. Fiber, however, plays a vital role in human health, aiding in digestion, controlling blood sugar levels, and promoting satiety. There are two main types of fiber:

Soluble Fiber: This dissolves in water and forms a gel-like substance in the stomach, which slows digestion and can help lower cholesterol and blood sugar. It is found in foods like oats, beans, and apples.
Insoluble Fiber: This type does not dissolve in water and adds bulk to the stool, promoting regular bowel movements. It is abundant in whole-wheat flour, nuts, and vegetables.

Understanding Sugar Alcohols

Sugar alcohols, also known as polyols, are a family of low-calorie sweeteners often used in “sugar-free” or low-carb processed foods like candy and chewing gum. Despite their name, they are neither sugar nor alcohol. They have a minimal impact on blood glucose because they are not fully absorbed by the body.

However, it's crucial to understand that not all sugar alcohols are created equal, and some are absorbed more than others. Erythritol, for instance, is poorly absorbed and has a negligible effect on blood sugar, so it is often fully subtracted. In contrast, maltitol has a higher glycemic impact, and it is generally recommended to subtract only half of its value. Consuming excessive sugar alcohols can also lead to digestive issues like gas, bloating, and diarrhea.

How to Calculate Net Carbs Step-by-Step

Calculating net carbs from a nutrition label is a straightforward process once you know the formula:

Net Carbs = Total Carbohydrates - Dietary Fiber - Sugar Alcohols (if applicable)

Find the Total Carbohydrates: Look for the "Total Carbohydrates" line on the nutrition label and note the serving size.
Locate Dietary Fiber: Find the "Dietary Fiber" listed under total carbohydrates. Subtract this number from the total carbs.
Check for Sugar Alcohols: If the label lists "Sugar Alcohols," you will need to adjust your calculation. For most sugar alcohols, subtract half the amount. For erythritol, you can typically subtract the full amount.
Perform the Calculation: Use the formula to get your final net carb count.

Example: A product has 20g Total Carbohydrates, 10g Dietary Fiber, and 8g of Sugar Alcohols (Maltitol). The calculation would be: 20g - 10g - (8g / 2) = 6g net carbs.

Total Carbs vs. Net Carbs Comparison


Feature	Total Carbohydrates	Net Carbohydrates
Definition	Includes all carbs: starches, sugars, fiber, and sugar alcohols.	Only includes digestible carbs that impact blood sugar.
Calculation	Read directly from the nutrition label.	Calculated by subtracting fiber and certain sugar alcohols from the total carbs.
Regulation	Regulated by the FDA in the U.S. and other food authorities.	Not officially defined or regulated by major health authorities.
Best For	General dietary tracking and for individuals with strict insulin needs, such as those with Type 1 diabetes.	People following low-carb, keto, or Atkins diets who need to limit their glycemic load.
Considerations	The safest, most consistent metric for those monitoring blood sugar.	Calculation relies on assumptions about sugar alcohol absorption, which can vary.

The Controversy and Practical Application

While the concept of net carbs is widely used in the low-carb community, it is not without controversy. Major health organizations like the American Diabetes Association do not officially recognize the term and often advise using total carbs for consistency, especially for those managing insulin. The effectiveness of net carb counting can vary by individual due to differences in metabolism and tolerance to sugar alcohols.

For those on a ketogenic diet, keeping a daily intake below 50 grams of net carbs is a common goal to maintain ketosis. Counting net carbs can allow for a broader range of fiber-rich, nutrient-dense vegetables that would otherwise seem too high in total carbs. However, relying solely on net carb counts on food packaging can be misleading, as some companies use less-than-accurate calculations.

Ultimately, whether you count net carbs or total carbs depends on your personal health goals. For most people, incorporating a variety of whole foods high in natural fiber is more beneficial than focusing on complex calculations for highly processed foods. For individualized guidance, especially if you have diabetes or other health conditions, consult a healthcare professional. A good starting point for learning more about fiber is the Mayo Clinic's detailed resource on the topic.

Conclusion

Understanding what gets subtracted from carbs is essential for anyone following a low-carb diet or simply trying to make more informed dietary choices. By removing the indigestible components like dietary fiber and select sugar alcohols, you can focus on the carbohydrates that truly impact your blood sugar. While the term "net carbs" is not officially regulated, it serves as a useful tool for managing carbohydrate intake when used correctly. Regardless of your counting method, prioritizing fiber-rich whole foods remains a cornerstone of healthy eating.

Frequently Asked Questions

To calculate net carbs, you take the total carbohydrates from a product's nutrition label and subtract the dietary fiber and, if present, the sugar alcohols. The full amount of fiber is subtracted, while the amount subtracted for sugar alcohols varies depending on the type.

Dietary fiber is a type of carbohydrate that your body cannot fully digest and absorb. Because it passes through your digestive system without being converted to glucose, it has a minimal impact on blood sugar levels and is therefore subtracted.

Not all sugar alcohols are treated equally. Some, like erythritol, are poorly absorbed and can be fully subtracted. Others, like maltitol and sorbitol, are partially absorbed and typically only half the amount is subtracted to get an accurate net carb count.

For individuals on low-carb or ketogenic diets, tracking net carbs can be beneficial for managing carbohydrate intake to stay in a fat-burning state known as ketosis. However, for general weight loss, focusing on overall calorie intake and nutrient-dense whole foods is most effective.

On a US nutrition label, you can find "Dietary Fiber" listed as a sub-item under "Total Carbohydrates." If the product contains sugar alcohols, they will also be listed under total carbohydrates.

The FDA and other major health organizations do not have a legal definition for the term "net carbs" because the glycemic impact of certain carbohydrates can vary by individual. They recommend using the total carbohydrate number for consistency and accuracy, especially for those with diabetes.

Many vegetables are naturally high in fiber with low net carbs. Good examples include leafy greens like spinach and kale, cruciferous vegetables like broccoli and cauliflower, avocados, and certain berries like raspberries and blackberries.