how to calculate net carbs

How to Calculate Net Carbs

The formula to calculate net carbs is as follows:

Total carbohydrates – (dietary fiber + sugar alcohols) = Net Carbs

Try out our Net Carbs Calculator Below ⬇️

Total Carbs:
Dietary Fiber:
Sugar Alcohols:
Net Carbs:

Why is Understanding Total Net Carbs Important?

If you are adhering to a low carbohydrate or keto type diet then paying attention to your net carb intake will help you achieve your macronutrient goals.

Net Carb Formula Breakdown

Total carbohydrates – (dietary fiber + sugar alcohols) = Net Carbs

Let’s break down the net carbs formula.  We’ll start with a hypothetical meal and calculate the total macronutrients consumed in the meal.  

Let’s say for lunch you eat an 8 oz chicken breast, a medium sized apple (approx. 100g), and a Quest Protein bar. 

The net carbs formula does not include protein or fats, so we don’t have to worry about them at all.

What we do have to account for are the total carbohydrates, dietary fiber, and sugar alcohols of the meal.

Here are the totals for each meal:

Chicken Breast: Total Carbs= 0g, Dietary Fiber= 0g, Sugar Alcohols= 0g

Apple: Total Carbs= 14g, Dietary Fiber= 2g, Sugar Alcohols= 0g

Quest Protein Bar: Total Carbs= 24g, Dietary Fiber= 14g, Sugar Alcohols= 6g

Meal totals: Total Carbs= 38g, Dietary Fiber= 16g, Sugar Alcohols= 6g

Now let’s apply our net carbs formula to our meal macros:

Total carbohydrates – (dietary fiber + sugar alcohols) = Net Carbs

38 – (16+6) 

38 – 22 = 16

Net Carbs = 16g

Why Do We Subtract Dietary Fiber From Net Carbs?

Fiber IS a type of carbohydrate, but your body lacks the necessary enzymes to break it down into usable energy. Therefore, fiber is not digested and it adds 0 calories and 0 carbohydrates to your diet. This is why they can be subtracted from total carbs when calculating net carbs.

Why do we subtract Sugar Alcohols from Net Carbs?

Sugar alcohols have a slightly different chemical structure than regular sugar, and therefore, the body cannot digest them.   Since they do not get digested, they do not add any extra calories or carbohydrates to your diet. They can be subtracted from total carbs to calculate net carbs.

Net Carb Formula Exceptions

Here is an excerpt from a, a popular health and wellness site, that goes into the details of which sugar alcohols can be completely subtracted from total carbs and which sugar alcohols can only be partially subtracted:

“The following sugar alcohols do not count toward net carbs for keto. If you’re eating something with these sweeteners, you don’t need to include them in your carb count:[1][2][3]

  • Erythritol
  • Xylitol
  • Mannitol
  • Lactitol

Exception: The sugar alcohols below do count (at least partially) toward net carbs:[4]

  • Maltitol
  • Sorbitol
  • Isomalt
  • Glycerin”

If you are consuming sugar alcohols from the the exception list above (maltitol, sorbitol, isomalt, glycerin) than you must use a different formula to calculate net carbs:

Grams of total carbs – (fiber + (sugar alcohols / 2)) = Net carbs

Calculate Net Carbs When Maltitol is your Sugar Alcohol

Let’s say you ate a Quest Protein bar and instead of the sugar alcohol erythritol, the manufacturers used the sugar alcohol maltitol instead.  Let’s calculate the net carbs in the quest bar:

Total carbs: 24g, dietary fiber= 14g, sugar alcohols(maltitol)= 6g

24 – (14 + (6/2)) = 7g

Net Carbs= 5g 


Understanding net carbs and how to calculate net carbs is important if you are trying to adhere to a low carb/keto type diet. There are many benefits that can result from a low carbohydrate diet such as body fat loss, improved body composition, improved hormonal profile, and more. If you’re interested in learning how to get into the best shape of your life, click here!

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