What the net carbs calculator does
Net carbs are the carbohydrates that raise blood sugar — total carbohydrates minus fibre and, where relevant, sugar alcohols, neither of which is digested into glucose. Anyone following a ketogenic or low-carb diet, or managing diabetes with carb counting, uses this number rather than the total on the label. Enter the figures from a nutrition label and the calculator returns net carbs per serving. It runs in your browser.
The formula
Net carbs = Total carbohydrates − Dietary fibre − Sugar alcohols (fully or partly, see below)
Label: 50 g total carbs, 10 g fibre, 5 g erythritol
Net carbs = 50 − 10 − 5 = 35 g
Label: 22 g total carbs, 12 g fibre, 0 sugar alcohols
Net carbs = 10 gWhy fibre is subtracted
Fibre is a carbohydrate by chemistry, which is why labels in the US and many other countries count it inside “total carbohydrate”, but humans lack the enzymes to break most of it into glucose. It passes to the colon, feeds gut bacteria and contributes little or nothing to blood sugar. Subtracting it gives a truer picture of a food's effect. Note that EU and UK labels already exclude fibre from the carbohydrate line and list it separately — on those labels, the carbohydrate figure is effectively already net.
Sugar alcohols: subtract with care
| Sugar alcohol | Glycaemic impact | How much to subtract |
|---|---|---|
| Erythritol | ≈ 0 | All of it |
| Allulose (not technically a sugar alcohol) | ≈ 0 | All of it |
| Xylitol | Low (GI ≈ 7–13) | About half |
| Sorbitol | Low–moderate (GI ≈ 9) | About half |
| Maltitol | Moderate (GI ≈ 35) | About half, or none if you are sensitive |
| Isomalt, mannitol | Low | About half |
Manufacturers of “keto” snacks often subtract all sugar alcohols to advertise a low net-carb figure. Maltitol in particular can raise blood sugar noticeably. If a product uses anything other than erythritol or allulose, subtracting only half is the safer assumption, and people with diabetes should test their own response.
Net carbs of common foods
| Food (per 100 g) | Total carbs | Fibre | Net carbs |
|---|---|---|---|
| Avocado | 8.5 g | 6.7 g | 1.8 g |
| Broccoli | 7 g | 2.6 g | 4.4 g |
| Raspberries | 12 g | 6.5 g | 5.5 g |
| Almonds | 22 g | 12.5 g | 9.5 g |
| Chia seeds | 42 g | 34 g | 8 g |
| Black beans, cooked | 24 g | 8.7 g | 15 g |
| Apple | 14 g | 2.4 g | 11.6 g |
| White rice, cooked | 28 g | 0.4 g | 27.6 g |
Daily targets by approach
- Ketogenic: typically 20–30 g net carbs per day, occasionally up to 50 g for active people.
- Low-carb: 50–100 g net per day — no ketosis, but meaningful blood-sugar and appetite effects.
- Moderate: 100–150 g — common for weight maintenance with less restriction.
- Diabetes carb counting: targets are individual and set with a clinician; many count total carbs and subtract fibre only when it exceeds 5 g per serving.