Net carbs is the number most keto and low-carb dieters track instead of total carbohydrates, because it tries to estimate only the carbs that meaningfully raise blood sugar. It isn't an official nutrition-label term — the FDA doesn't define or require it — so different brands and apps sometimes calculate it slightly differently. This calculator uses the two most common conventions.
How the net carbs formula works
Net carbs starts from "Total Carbohydrate" on the nutrition facts label, then subtracts two categories that have less impact on blood sugar than starches and sugars do. Dietary fiber is always subtracted in full, since it passes through the digestive system largely unmetabolized. Sugar alcohols are more complicated: most (sorbitol, maltitol, xylitol) are partially absorbed and carry a partial glycemic impact, so the standard convention only subtracts half their gram weight. A stricter "full" method subtracts all of it instead, which some trackers prefer as a conservative estimate.
Total carbs, fiber, and sugar alcohols
All three inputs come straight off the nutrition facts panel and are measured in grams. Total carbohydrates and fiber are required — every US label carries both. Sugar alcohols is optional; leave it at 0 if the label doesn't list any (most whole foods and many packaged foods won't). The input that moves the result most is usually fiber for whole foods, and sugar alcohols for sugar-free or low-carb packaged products.
Limits and edge cases
Net carbs is a diet-tracking convention, not a clinically validated measure of actual blood-sugar response — individual responses to fiber and sugar alcohols vary by person and by the specific sweetener used. Erythritol is a common source of confusion: because it's almost entirely unabsorbed, many products already exclude it from "Total Carbohydrate" on the label, in which case subtracting it again here would double-count the deduction. Large amounts of sugar alcohols can also cause digestive discomfort in some people regardless of their net-carb math. This tool is informational only — check with a registered dietitian if net carbs is central to a medical nutrition plan.