Figuring Out "Net Carbs"
Calculating Net Carbs in Whole Foods
Whole foods contain naturally occurring fiber. Therefore, you can simply subtract the fiber from the total carbs to get the net carbs.
The USDA Food Composition Databases Trusted Source provides complete nutrition information on thousands of foods, including carbs and fiber.
For example, a medium avocado contains 17.1 grams of total carbs, 13.5 grams of which is fiber.
So 17.1 grams of total carbs – 13.5 grams of fiber = 3.6 grams of net carbs.
Calculating Net Carbs From Fiber
Most fiber can be completely subtracted from the total carbs listed on the nutrition label.
If you live outside the US, the “total carbohydrate” line already has the fiber removed and listed separately.
However, if the fiber isomaltooligosaccharide (IMO) is in the ingredients list, subtract only half of the fiber carbs.
Calculating Net Carbs From Sugar Alcohols
Generally speaking, half of the carbs from sugar alcohols can be subtracted from the total carbs listed on the nutrition label.
Erythritol is an exception. If it’s the only sugar alcohol in the ingredients list, its carbs can be completely subtracted from the total carbs.
This value may be different than the number of net carbs stated on the product label, since many companies subtract all fiber and sugar alcohol carbs when calculating net carbs.
For example, a maltitol-sweetened Atkins bar label states that it contains 3 grams of net carbs.
However, when subtracting only half the carbs from sugar alcohols, the net carb value is 8.5 grams: 23 grams of total carbs – 9 grams of fiber – 11 grams sugar alcohols (11 grams X 0.5 = 5.5 grams) = 8.5 grams of net carbs.
SUMMARY:A portion of fiber and sugar alcohols can be subtracted from total carbs to calculate net carbs. Formula: total carbs minus fiber (or half of IMO) minus half the carbs from sugar alcohols (other than erythritol) = net carbs.
Reference: How to Calculate Net Carbs (healthline.com)