Net Carb Calculator

Net carbs = total carbohydrates − fiber − sugar alcohols that your body doesn’t meaningfully absorb. Fiber passes through largely unprocessed, so keto and low-carb eaters count what remains. The catch is that "sugar alcohols" aren’t one thing — some earn the subtraction and some don’t, which is why a blanket subtraction produces a fictional number.

Some do. Erythritol and allulose have close to zero glycemic impact — subtracting them fully is fair. Maltitol is the problem child: it carries roughly half the glycemic impact of table sugar, so an honest count subtracts only about half of it. Sorbitol, isomalt, and xylitol sit in between and also deserve partial counting. Any product leaning on maltitol while advertising a low net-carb number is doing marketing, not math.

Usually one of three reasons: the label subtracted all of its maltitol, the serving size assumes you ate a fraction of what a human eats, or your individual response simply differs from the average the label was built on. This is exactly why metabomap exists — log the food, log your glucose reading, and see what that product does to you rather than what the package claims. The label proposes; your meter disposes.

Opinions differ honestly: net carbs reward fiber-rich whole foods, while total carbs are stricter and immune to label games. Our answer is that you shouldn’t have to choose — metabomap shows both numbers side by side on every food, every meal, every day, so you can hold whichever line you’ve picked and see the other at a glance. Both are in the free tier.

Dietary fiber isn’t digested into glucose, which is why it subtracts. Two cautions: it only subtracts on US-style labels (EU-style labels never included it in the carb line), and "isolated" fibers added to processed keto products vary in how inert they really are — one more reason the label is a starting point, not a verdict.

Mostly no, and we say that as people who run one. Crowdsourced databases are full of entries where fiber or sugar alcohols were typo’d, doubled, or invented — and one wrong fiber number breaks the whole calculation. metabomap builds on USDA-backed data, marks every row’s source and trust tier, keeps user-created foods out of global search until verified, and commits to auditing against real labels and publishing the results on our public Our Data page.