Net Carb Calculator
Use our net carb calculator to calculate the number of net carbohydrates in a meal, ingredient, or serving, given the total carbs, dietary fiber, and sugar alcohol in grams.
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What Are Net Carbs?
You can’t talk about a very low-carbohydrate or ketogenic diet without discussing net carbohydrates.
When you eat carbohydrates, these are broken down into the components of sugar, such as glucose and fructose. The body then absorbs these through the small intestine.
However, some carbohydrates, like fiber, can’t be broken down into individual sugars and instead of being absorbed, are fermented in the large intestine. Other carb sources, such as sugar alcohols, are only partially broken down and absorbed.
Due to this, it is thought that most fiber and sugar alcohols can be subtracted from the total carb content of a food to give a “net carb” value instead. While the FDA does not regulate this term, the USDA has implemented a policy that it can be used so long as the claim is truthful, not misleading, and supported by calculations shown on the label.
Net carbs are sometimes also referred to as “impact carbs,” “effective carbs,” or “net effective carbs.” It is thought that since sugar alcohols, fiber, and glycerin have minimal effect on blood glucose, they can be subtracted from the total carbohydrate count. This would lower the overall content of a food containing fiber or sugar alcohols.
Unfortunately, this calculation can underestimate the actual carbohydrate value in many foods. Not only can this affect someone counting keto macros to follow in their diet, but it can also lead to miscalculating insulin dosages for individuals with diabetes that are counting carbohydrates.
How To Calculate Net Carbs for Keto Macros
As noted above, sugar alcohols should be considered to have about 2 calories per gram in contrast to 4 calories per gram of fully absorbed carbs. Therefore, half of the carbs from sugar alcohols can be subtracted from the total carbs listed on the nutrition label.
One exception is erythritol. If it’s the only sugar alcohol on the list of ingredients, then its carbs can be removed from the total carbs since it contains only about 0.2 kcal/g.
Most fiber can be entirely subtracted from the carbs listed on the nutrition label since this is not absorbed in the small intestine and contributes minimally to blood glucose levels.
Net Carbs Formula
This is the resulting net carbs formula:
net carbs = total carbs – dietary fiber – (sugar alcohol ÷ 2)
Net carbs are equal to the total carbs minus the dietary fiber minus the sugar alcohol divided by 2.
Net Carbs or Total Carbs?
The big question becomes, should you count total carbs or net carbs when counting keto macros?
One reason to count net carbs is that it can make it easier to increase healthy food choices. Many healthy fruits and vegetables may seem high in carbs, however this is because they are mainly composed of fiber.
More of these can be included in a healthy, balanced keto diet if you use the net carb method.
These can still be included in a healthy, balanced keto diet if you don’t count these fiber calories towards the restrictive carb count.
One of the biggest drawbacks of a keto diet is that it can be low in fiber. By using the net carb approach, this will lead to higher fiber intake.
This is important for overall health and weight loss. Fiber-rich foods decrease appetite, improve blood sugar and cholesterol levels, enhance gastrointestinal health, and decrease calorie absorption.
However, there is also a downside to using net carbs over total carbs in your macro counting.
First of all, due to the varying calories per gram of specific sugar alcohols, this method is not 100% accurate. In addition, each individual digests and absorbs fiber at a different rate, which can affect the actual impact of carbohydrates.
Since calculating net carbs is not completely accurate, it could lead to an overconsumption of carbohydrates and ultimately hamper weight loss and increase the risk of chronic health issues.
It can also lead to a high intake of processed “sugar-free” foods. However, overeating products that are marketed as “low in net carbs” can actually cause gastrointestinal distress and are usually processed foods.
In the end, counting net carbs may be a good choice for some people, while others may do better using a total carb count. The best course is to choose whole foods with high fiber, such as fruits and vegetables, rather than packaged foods with high amounts of sugar alcohols.
Additionally, because this diet can be restrictive and confusing, working with a professional while following this diet can assure that the diet is right for you and your specific health needs.
Sugar alcohols are hydrogenated carbohydrates that are used in foods as sweeteners. This includes ingredients like sorbitol, mannitol, xylitol, and erythritol. While these sugar alcohols are not completely reabsorbed, they are not calorie-free, as many people believe.
They actually provide around 0.2–3 calories per gram (or kcal/g), which is only slightly less than the usual 4 calories per gram from fully absorbed carbohydrates. FDA regulations require that food manufacturers count sugar alcohols as 2 calories per gram or use the specific kcal/g value determined by the FDA for a single-sugar alcohol.
Since these sugar alcohols are not completely reabsorbed, they can cause gastrointestinal disturbances such as flatulence or loose stools.
One guideline for counting sugar alcohols in your carbohydrate count is to subtract half of the grams of total sugar alcohols listed from the total carbohydrate value. In addition, if a “sugar-free” food has less than 5 grams of carbohydrate or less than 20 kcal/serving, it is unnecessary to count the carbohydrate from the sugar alcohol.
Glycerin, or glycerol, is a sweet, syrupy liquid that contains 4.32 kcal/g. This is used as a food additive in a number of products, including nutrition or energy bars.
The FDA states that glycerin must be included in the grams of total carbohydrate listed in the Nutrition Facts panel. If the label has a statement regarding sugars, the FDA requires the glycerin content per serving to be declared as sugar alcohol.
Dietary fiber is not digested and absorbed in the small intestine like glucose. Fiber is broken down, or fermented, in the large intestine to produce fatty acids.
These are then absorbed and used as energy. There are two forms of fiber, soluble and insoluble forms.
Soluble fiber is made up of hemicelluloses and pectins and is found in fruits and vegetables. Insoluble fiber made up of cellulose is less fermentable than soluble fiber and is found in foods like whole grains and cereals.
The estimated energy that comes from fiber is between 1.5 and 2.5 kcal/g, which is slightly less than the 4 calories per gram from fully digested and absorbed carbohydrates.
- Freeman, J., & Hayes, C., 'Low-carbohydrate' food facts and fallacies, Diabetes Spectrum, 2004, 17(3), 137-140. https://spectrum.diabetesjournals.org/content/17/3/137
- Diabetes Education Online - University of California, Counting Sugar Alcohols, https://dtc.ucsf.edu/living-with-diabetes/diet-and-nutrition/understanding-carbohydrates/counting-carbohydrates/learning-to-read-labels/counting-sugar-alcohols/
- CFR - Code of Federal Regulations Title 21, https://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfcfr/CFRSearch.cfm?fr=101.9
- Crosby, L., Davis, B., Joshi, S., Jardine, M., Paul, J., Neola, M., & Barnard, N. D., Ketogenic Diets and Chronic Disease: Weighing the Benefits Against the Risks, Frontiers in Nutrition, 2021, 8, https://doi.org/10.3389/fnut.2021.702802