What net carbs actually means on keto
June 7, 2026 · 3 min read
If you've started keto, you've run into two numbers on every label: total carbohydrate and, underneath it, fiber. The number that matters for staying in ketosis is neither of those on its own — it's the difference between them, usually called net carbs.
The simple formula
Net carbs is total carbohydrate minus the carbs your body doesn't turn into usable glucose:
- Net carbs = total carbohydrate − fiber − sugar alcohols (mostly)
Fiber passes through largely undigested, so it doesn't raise blood sugar. Most sugar alcohols (like erythritol) are absorbed poorly and have little glycemic impact. What's left — the net number — is the part that actually counts against your daily carb ceiling.
Why keto cares about this number
A ketogenic diet works by keeping usable carbohydrate low enough that your body shifts to burning fat for fuel. Total carbohydrate overstates how much you actually absorbed; net carbs is the closer estimate. Two foods with the same total carbs can land very differently:
| Food | Total carbs | Fiber | Net carbs |
|---|---|---|---|
| 1 cup raspberries | 15 g | 8 g | 7 g |
| 1 slice white bread | 14 g | 1 g | 13 g |
Same total, very different impact on ketosis.
Where labels mislead you
- Not all sugar alcohols are equal. Erythritol is nearly free; maltitol raises blood sugar meaningfully. Subtracting the full amount of maltitol is how "keto" candy knocks you out of ketosis.
- "Keto" on the front means nothing. It isn't a regulated term. Read the actual numbers.
- Serving sizes are small on purpose. Double the serving, double the carbs.
The honest version
Net carbs is an estimate, not a law of physics — bodies vary. The point isn't to litigate every gram; it's to have one consistent number you track against your ceiling so you can see what's actually moving you toward your goal. If you want the primary research behind fiber, sugar alcohols, and glycemic response, it's collected in the carb-science sources.
That's the whole job of Copper Keto Companion: you say what you ate, it works out the net carbs, and it tells you the truth — without turning the math into another chore.
Common questions
Do sugar alcohols count as net carbs? Most sugar alcohols can be subtracted on US labels because they have minimal blood sugar impact. The exception is maltitol — it has a glycemic index of 35–52 and does raise blood glucose, so subtract it with caution. Erythritol (GI ~0) is the safest to subtract.
Is net carbs the same as digestible carbs? Roughly, yes. Net carbs is the US label convention (total carbs minus fiber minus most sugar alcohols). "Digestible carbs" is the underlying concept. The two terms are used interchangeably in most keto contexts.
What about fiber on UK labels? UK nutrition labels already list carbohydrates excluding fiber — so the number on the label is already the net carb figure. No subtraction needed. US labels include fiber in the total carbohydrate number, which is why US readers subtract it.