What Are Net Carbs? How to Calculate Them (2026)
Net carbs explained simply: the formula (total carbs minus fiber and sugar alcohols), why it matters for keto, and worked examples you can use today.
Head of Nutrition · June 9, 2026 · 2 min read
Last updated June 10, 2026
Net carbs are the carbohydrates your body actually digests and turns into blood glucose. You calculate them by subtracting fiber and sugar alcohols from total carbohydrates, because those pass through largely undigested. Net carbs are the number most keto and low-carb diets track, and they're usually lower than the "total carbs" on the label.
The net carbs formula
Net carbs = Total carbohydrates − Fiber − Sugar alcohols
Total carbs include starches, sugars, and fiber. Fiber and most sugar alcohols have little effect on blood sugar, so low-carb diets subtract them.
Why fiber is subtracted
Fiber is a carbohydrate your body can't fully break down, so it doesn't spike blood glucose the way starch or sugar does. The Mayo Clinic notes that dietary fiber passes relatively intact through your digestive system, which is exactly why it's removed from the net carb count. A cup of raw spinach has about 1g of total carbs, almost all fiber, so its net carbs round to roughly zero.
What about sugar alcohols?
Sugar alcohols (erythritol, xylitol, maltitol) are common in "keto" snacks and are only partially digested, so the rules vary:
| Sugar alcohol | Subtract? | Why |
|---|---|---|
| Erythritol | Full amount | Almost entirely unabsorbed |
| Xylitol | Most of it | Minimal blood-sugar impact |
| Maltitol | Little or none | Raises blood sugar more than the label suggests |
When in doubt, test how a food affects you rather than trusting the package math.
A worked example
A serving of almonds shows 6g total carbs and 3g fiber. Net carbs = 6 − 3 = 3g. That's why nuts fit comfortably into most low-carb days while bread, with little fiber relative to its starch, does not.
Why net carbs matter for keto
Staying in ketosis depends on keeping digestible carbs low. Standard ketogenic diets restrict carbohydrates to under 50g per day, and stricter versions to 20–30g (National Library of Medicine). Counting total carbs instead would make that limit feel impossibly strict and push you away from healthy, high-fiber vegetables.
Key takeaways
- Net carbs = total carbs − fiber − sugar alcohols.
- Fiber and erythritol are subtracted; maltitol usually isn't.
- Keto diets target ~20–50g net carbs per day.
- An app that subtracts automatically removes the daily math.
The easiest way to stay consistent is to let an app do the subtraction for you. CarbMeNot calculates net carbs every time you log a food, so you always know how much room you have left for the day.
Frequently asked questions
- What are net carbs?
- Net carbs are the carbohydrates your body digests into glucose. You calculate them by taking total carbohydrates and subtracting fiber and sugar alcohols, because those pass through largely undigested and have little effect on blood sugar.
- How do you calculate net carbs?
- Net carbs = total carbohydrates − fiber − sugar alcohols. For example, a food with 6g total carbs and 3g fiber has 3g net carbs.
- Do net carbs matter for keto?
- Yes. Most ketogenic diets cap net carbs at roughly 20–50g per day. Tracking net carbs (rather than total carbs) lets you eat high-fiber vegetables while still staying in ketosis.
- Should you subtract sugar alcohols from carbs?
- Subtract erythritol fully (it's almost entirely unabsorbed). Subtract maltitol cautiously or not at all, since it raises blood sugar more than its label implies.
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