Net Carbs vs Total Carbs: What Actually Counts on Keto?
On keto, the carbohydrate number that matters is net carbs — the carbs your body actually digests into glucose. Working them out is a simple subtraction once you know what to take out, but food labels make it confusing by counting things differently on each side of the Atlantic. Here is exactly how to do it.
What are net carbs?
Net carbs are the total carbohydrate in a food minus the parts that don't raise your blood sugar — mainly fiber, and most sugar alcohols.
Net carbs = Total carbohydrate − Fiber − most sugar alcohols
Those subtracted grams still show up on the label under "carbohydrate", but your body either can't break them down into glucose or barely does. So they don't spike your blood sugar or pull you out of ketosis the way starch and sugar do. That's why keto plans — and this calculator — count net carbs rather than total carbs.
Why fiber doesn't count
Total carbohydrate is really net carbs plus fiber. Net carbs are the part that turns into glucose and raises blood sugar — exactly what you want to limit, which is why most people aim for 20–25 g a day. Fiber is the rest, and it is good for you. Insoluble fiber passes straight through without touching your blood sugar, while gut bacteria ferment soluble fiber into short-chain fatty acids that add only a few calories and don't spike glucose. So keto counts net carbs and lets fiber off the hook.
Worked examples
Whole, keto-friendly foods are mostly fiber once you do the subtraction. A few common ones, per typical serving:
| Food | Serving | Total | Fiber | Net |
|---|---|---|---|---|
| Broccoli | 1 cup (90 g) | 6 g | 2.4 g | 3.6 g |
| Avocado | 100 g | 9 g | 7 g | 2 g |
| Almonds | 1 oz (28 g) | 6 g | 3.5 g | 2.5 g |
| Raspberries | ½ cup (60 g) | 7 g | 4 g | 3 g |
| Chia seeds | 2 tbsp (24 g) | 10 g | 8 g | 2 g |
The pattern is clear: a food can look carb-heavy on its total line and still be a low net-carb choice once the fiber comes out. It works the other way too — bread, rice and sugar have almost no fiber, so their net carbs are close to their total.
Sugar alcohols: not all of them are free
Sugar alcohols (polyols, listed on labels as erythritol, maltitol, xylitol and so on) are the one place the subtraction gets fiddly. They are not all the same:
- Erythritol and allulose have essentially no effect on blood sugar — subtract them in full.
- Maltitol does raise blood sugar noticeably — count roughly half its grams, or all of them if you're strict.
- When a product just says "sugar alcohols" and you can't tell which, the safe move is to count them.
This is why two "low-carb" treats with the same net-carb claim can affect ketosis very differently — read which sweetener they actually use.
US vs European food labels
The biggest source of confusion is that the two label systems already count carbs differently:
- United States: the "Total Carbohydrate" line includes fiber. You subtract the fiber (and any free sugar alcohols) yourself to get net carbs.
- Europe and the UK: the "Carbohydrate" line already excludes fiber, which is listed separately. So a European carbohydrate figure is already net carbs — no subtraction needed.
In short: a US label needs the math; a European label has mostly done it for you.
How this fits your macros
The carb field in the keto calculator is net carbs, and it starts you at 25 g a day — a level most people stay in ketosis on. When you track what you eat, subtract the fiber (and the free sugar alcohols) so you're comparing like with like against that target.
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