Health & Fitness · Guide
How to Calculate Net Carbs (Keto and Atkins)
Total carbs minus fibre minus most sugar alcohols. Simple — once you know which label you are reading.
Want the answer for your own numbers? Use the free Carbohydrate Calculator — it does every step below for you.
What are net carbs?
Net carbs are the carbohydrates your body actually digests into sugar. Fibre passes through mostly undigested, and many sugar alcohols are only partly absorbed. Low-carb diets like keto and Atkins count net carbs because they have the biggest effect on blood sugar and ketosis.
"Net carbs" is a diet term, not an official nutrition term. The US FDA does not define it, so food companies can calculate it in different ways. Doing it yourself is the safest route.
The net carbs formula
Net carbs = total carbohydrate − dietary fibre − sugar alcohols*
*Subtract erythritol in full. For most other sugar alcohols (maltitol, sorbitol, xylitol), many people subtract only half, because they are partly absorbed and can raise blood sugar.
Step-by-step on a US label
Example: a protein bar
Total carbohydrate 24 g. Dietary fibre 10 g. Sugar alcohols 8 g (erythritol).
24 − 10 − 8 = 6.
Net carbs = 6 g
If the 8 g were maltitol instead, subtract half (4 g): 24 − 10 − 4 = 10 g net.
The UK and EU label trap
On UK and EU labels, the "carbohydrate" figure already excludes fibre. Fibre is listed separately. So the carbohydrate line is already close to net carbs. Do not subtract the fibre again, or you will undercount.
| Label | "Carbohydrate" includes fibre? | What to do |
|---|---|---|
| US, Canada | Yes (total carbohydrate) | Subtract fibre and sugar alcohols |
| UK, EU, Australia | No | Subtract only sugar alcohols (if listed as polyols) |
Net carbs in common foods
| Food (100 g) | Total carbs | Fibre | Net carbs (approx.) |
|---|---|---|---|
| Avocado | 8.5 g | 6.7 g | 1.8 g |
| Broccoli, raw | 6.6 g | 2.6 g | 4.0 g |
| Almonds | 21.6 g | 12.5 g | 9.1 g |
| Raspberries | 11.9 g | 6.5 g | 5.4 g |
| Apple, with skin | 13.8 g | 2.4 g | 11.4 g |
| White rice, cooked | 28.2 g | 0.4 g | 27.8 g |
Values are typical figures from USDA FoodData Central and vary by variety.
A few more everyday foods, per 100 g:
| Food (100 g) | Total carbs | Fibre | Net carbs (approx.) |
|---|---|---|---|
| Spinach, raw | 3.6 g | 2.2 g | 1.4 g |
| Cauliflower, raw | 5.0 g | 2.0 g | 3.0 g |
| Strawberries | 7.7 g | 2.0 g | 5.7 g |
| Chia seeds | 42.1 g | 34.4 g | 7.7 g |
| Sweet potato, baked | 20.7 g | 3.3 g | 17.4 g |
| Banana | 22.8 g | 2.6 g | 20.2 g |
Chia seeds are the surprise: 42 g of total carbs, but most of it is fibre, so the net figure is under 8 g.
Sugar alcohols compared
Not all sugar alcohols behave the same. Their calories per gram give a clue to how much your body absorbs:
| Sweetener | Calories per gram (approx.) | How much to subtract |
|---|---|---|
| Erythritol | 0.2 | All of it |
| Xylitol | 2.4 | Half |
| Sorbitol | 2.6 | Half |
| Maltitol | 2.1 | Half, or none if you are cautious |
| Regular sugar, for comparison | 4 | None |
Maltitol is the one to watch. It is common in “sugar-free” chocolate and can raise blood sugar noticeably. Large amounts of most sugar alcohols can also upset your stomach.
Example on a UK label
Per 100 g: carbohydrate 12 g, of which polyols 5 g (erythritol), fibre 8 g
Fibre is already left out of the 12 g, so do not subtract it.
Subtract the erythritol in full: 12 − 5 = 7.
Net carbs = 7 g per 100 g
On a US label the same product would show about 20 g total carbohydrate, because fibre is included — and you would reach the same 7 g after subtracting both.
How many net carbs on keto and Atkins?
- Keto: most plans keep net carbs around 20–50 g a day, many aiming for 20–30 g at the start.
- Atkins 20: starts at about 20 g net carbs a day, then adds carbs back in stages.
- Atkins 40: starts at about 40 g net carbs a day.
To see how your carbs fit with protein and fat, choose the Ketogenic preset in the carbohydrate calculator. It works in total carbs, so subtract fibre as shown above.
If you have diabetes or take medicine that lowers blood sugar, speak to your doctor before starting a very low-carb diet. Medicine doses may need to change.
Frequently asked questions
Subtract dietary fibre and sugar alcohols from total carbohydrate. A food with 24 g total carbs, 10 g fibre and 8 g erythritol has 6 g net carbs. Subtract only half of sugar alcohols such as maltitol.
No. UK and EU labels already exclude fibre from the carbohydrate figure, so subtracting it again would undercount your carbs.
Most keto and Atkins plans use net carbs, because fibre has little effect on blood sugar. Tracking total carbs is stricter and simpler, and some people with diabetes or slow progress prefer it. Pick one method and use it consistently.
Allulose is a rare sugar, not a sugar alcohol. It appears in total carbohydrate on US labels but is barely absorbed, so most low-carb plans subtract it in full, like erythritol. It still has a small number of calories, about 0.4 per gram.
Sources and further reading
- USDA FoodData Central — carbohydrate and fibre values for foods