Net Carbs Calculator
Total carbohydrate minus fiber, with the sugar-alcohol handling as an explicit labeled choice rather than a hidden assumption. For planning daily carbohydrate alongside protein and fat, see the Macro Calculator; for the calorie budget those grams live inside, the Calorie Calculator.
From the label to net carbs
Example: 30 g total − 10 g fiber = 20 g net; with 10 g sugar alcohols at half → 15 g.
The arithmetic, and whose rules it follows
Start from a US-style label, where fiber and sugar alcohols sit inside total carbohydrate. A food with 30 g total and 10 g fiber has 20 g net carbs; add 10 g of maltitol handled at the common half convention and the figure drops to 15 g — both computed by the same tested engine as the calculator. Every subtraction here is a convention: fiber in full because it largely escapes absorption in the small intestine, erythritol in full because it leaves the body unmetabolized, other sugar alcohols at half because "partially digested" got rounded to a factor of 0.5 by practice, not by a study. The dropdown exists so that choice is yours and visible.
Reading the label without double-counting
Two traps produce most wrong answers. First, "sugars" is not "sugar alcohols" — sugars are ordinary carbohydrate and need no adjustment. Second, EU-style labels already exclude fiber from the carbohydrate line, so subtracting fiber again undercounts; in that case enter the carbohydrate figure and leave the fiber field empty. If fiber plus sugar alcohols exceed the total you typed, the calculator refuses rather than inventing negative carbohydrate.
Frequently asked questions
What are net carbs?
A labeling convention from low-carb practice: total carbohydrate minus the carbohydrate assumed not to raise blood glucose meaningfully — fiber, and some or all sugar alcohols. It is not a regulated term or a settled scientific quantity, and different products compute it differently.
Why is erythritol treated differently from other sugar alcohols?
Most ingested erythritol is absorbed but not metabolized and leaves in urine, so the convention subtracts it in full. Other sugar alcohols — maltitol, sorbitol, xylitol, isomalt — are partially digested and do raise blood glucose somewhat, so the common convention subtracts only half. Individual responses vary either way.
Why can the subtractions not exceed total carbs?
On a nutrition label, fiber and sugar alcohols are components of the total-carbohydrate line. If their sum exceeds the total, the label has been misread (for example, taking "sugars" for "sugar alcohols") — the calculator flags it rather than producing negative carbs.
Do labels in every country work the same way?
No. US labels include fiber inside total carbohydrate, which this calculator assumes. EU-style labels state carbohydrate excluding fiber, so subtracting fiber again would double-count it — with an EU label, enter the carbohydrate figure directly and leave fiber at zero.
Should people with diabetes use net carbs for insulin dosing?
Not from this page. Carbohydrate counting for insulin dosing is clinical territory where the fiber and sugar-alcohol adjustments are individualized by a care team. This calculator applies a popular labeling convention for general food comparison — that is a different job.
Not medical advice: "net carbs" is a food-labeling convention, and individual glycemic responses to fiber and sugar alcohols vary. Anyone counting carbohydrate for medical reasons — insulin dosing above all — should follow their care team's method, not this convention. Data is processed locally in your browser and never transmitted. See the methodology page.