Net Carbs Calculator
Find net carbs for keto tracking by subtracting fiber and half of sugar alcohols from total carbs.
Low-carb and keto eaters track net carbs — the carbs that actually raise blood sugar. Fiber passes through undigested, so you subtract it fully. Sugar alcohols like erythritol or maltitol are only partly absorbed, so a common rule of thumb subtracts half of them.
The half-subtraction for sugar alcohols is an approximation; erythritol is often counted as zero while maltitol raises blood sugar more. Estimate, not medical advice.
How it works
Net carbs are the carbs that actually raise your blood sugar, which is what low-carb and keto eaters care about. The formula is simple: total carbohydrates minus fiber minus half of your sugar alcohols.
Fiber is subtracted in full because your body doesn't digest it for energy. Sugar alcohols like erythritol, xylitol, and maltitol are only partly absorbed, so a common rule of thumb removes half of them rather than all or none.
Take a keto bar with 22 g total carbs, 8 g fiber, and 6 g sugar alcohols. Subtract the 8 g of fiber and 3 g (half of the sugar alcohols) and you land at 11 g net carbs — a very different number from the 22 g on the front of the label.
Frequently asked questions
Why only subtract half the sugar alcohols?
Because most sugar alcohols are partially digested. Halving them is a middle-ground rule of thumb. Erythritol is often counted as zero since it's barely absorbed, while maltitol raises blood sugar more, so adjust if you know which one you're eating.
Is counting net carbs recognized everywhere?
It's popular in the U.S. for keto and low-carb diets, but some countries and dietitians only use total carbs on labels. Net carbs are a practical tracking tool, not an official regulatory figure.
Should I count fiber and sugar alcohols the same way for everyone?
Not necessarily. People react to sugar alcohols differently, and some raise blood sugar more than others. Use this as a starting estimate and adjust based on how your own body responds.