Net Carbs

Net Carbs — Net carbs is an unofficial nutritional metric calculated by subtracting fiber and sugar alcohols from total carbohydrates on a food label. The concept is intended to estimate the carbohydrate fraction that meaningfully raises blood glucose, but the term has no FDA-recognized regulatory definition and is used inconsistently across the industry.

What are net carbs?

“Net carbs” (sometimes called “impact carbs” or “active carbs”) is a marketing-derived metric, not a regulatory one. The most common formula is:

Net carbs = total carbohydrate − dietary fiber − sugar alcohols

The reasoning is that dietary fiber is largely indigestible (passes through without producing glucose) and that sugar alcohols (erythritol, xylitol, maltitol) are partially absorbed and produce a smaller glucose response than equivalent grams of sucrose or glucose.

The term is heavily associated with low-carb and ketogenic diets, where practitioners typically aim for <20 to <50 grams of net carbs per day rather than total carbs.

How accurate is the net carb concept?

The fiber subtraction is reasonably well supported. Insoluble fiber and many fermentable fibers do not significantly raise blood glucose, and USDA FoodData Central reports fiber separately for this reason.

The sugar alcohol subtraction is less defensible. Erythritol is essentially zero-glucose-impact, but maltitol has a glycemic index of approximately 35-50 and produces a meaningful glucose response. Counting all sugar alcohols as zero is misleading.

The FDA does not recognize “net carbs” on the Nutrition Facts panel. Total carbohydrate is the regulated value.

Why net carbs matter

For users on a ketogenic or low-carb plan, net carbs is the operative tracking metric because it more closely approximates the carbohydrate load that affects ketosis and blood glucose. For general weight management or for diabetics, however, tracking total carbs (and considering glycemic load) is more conservative and avoids being misled by maltitol-heavy “keto” packaged foods.

Most modern calorie tracking apps now display both total and net carbs as a configurable preference. See macronutrient for a broader discussion of macro tracking.