What Are Net Carbs?
Net carbs (also called digestible or impact carbs) represent the carbohydrates your body actually absorbs and converts into glucose. Because dietary fiber is not digested and sugar alcohols are only partially metabolized, they are subtracted from the total carbohydrate count. This Net Carbs Calculator is popular with people following keto, Atkins, and other low-carb diets who track impact carbs rather than total carbs.
How to Use This Calculator
Read the Nutrition Facts label on your food and enter three values: Total Carbohydrates, Dietary Fiber, and Sugar Alcohols (often listed as erythritol, xylitol, maltitol, etc.). All figures are in grams. Press calculate and the tool returns your net carbs instantly. If the result would be negative, it is clamped to zero.
The Formula Explained
The calculator uses the common low-carb formula:
$$\text{Net Carbs} = \text{Total Carbs} - \text{Fiber} - \frac{\text{Sugar Alcohols}}{2}$$
Fiber is fully subtracted because it passes through largely undigested. Sugar alcohols are subtracted by half, since most (like maltitol) raise blood sugar moderately, so only about 50% of their carbs are counted as impactful. Note: erythritol has almost no glycemic impact, so some people subtract it entirely — adjust your inputs if you prefer.
Worked Example
Suppose a protein bar has 24 g total carbs, 9 g fiber, and 8 g sugar alcohols. $$\text{Net Carbs} = 24 - 9 - \left(8 \div 2\right) = 24 - 9 - 4 = \textbf{11 g}$$ of net carbs.
FAQ
Why subtract only half the sugar alcohols? Many sugar alcohols are partially absorbed and raise blood glucose, so counting half is a common conservative estimate.
Do I always subtract all the fiber? In the US, total fiber is typically subtracted in full. Some regions already exclude fiber from listed carbs — check your label.
Can net carbs be negative? No. If the math yields a negative number, your net carbs are effectively zero.
