About the Net Carbs Calculator
Net carbs are the carbohydrates your body digests into glucose — total carbohydrate minus the parts that pass through largely unabsorbed, mainly fiber and some sugar alcohols. Keto and low-carb dieters count net carbs because a high-fiber food can list plenty of total carbs yet have little effect on blood sugar or ketosis.
Enter the numbers from the nutrition facts panel. The calculator handles the two common label styles: US labels include fiber inside “Total Carbohydrate”, so fiber is subtracted, while EU, UK and Australian labels already list carbohydrate without fiber, so only sugar alcohols are removed. You can choose how much of the sugar alcohols to subtract, because erythritol is barely absorbed while maltitol and sorbitol are partly digested.
“Net carbs” is not a term defined by the FDA, so product claims vary. The conservative convention used here — subtract all fiber, all erythritol and allulose, but only half of other sugar alcohols — is widely used by dietitians and keto resources.
With the default inputs, the net carbs per serving is 12 g. Change any value above to recalculate instantly.
How to use the net carbs calculator
- 1Choose the label style — US/Canada or EU/UK/Australia.
- 2Enter total carbohydrate, fiber and sugar alcohols per serving from the label.
- 3Pick the sugar alcohol type (erythritol vs others) and add any allulose.
- 4Enter how many servings you eat.
- 5Read net carbs per serving and in total for your log.
Formula and method
On US labels, Total Carbohydrate already includes fiber, sugar alcohols and allulose, so each is subtracted. On EU, UK and Australian labels, the carbohydrate figure excludes fiber but includes polyols, so only sugar alcohols and allulose are removed and the fiber you enter is ignored.
The factor s is how much of the sugar alcohol is treated as unabsorbed: 100% for erythritol (almost none is metabolised), 50% for maltitol, sorbitol, xylitol and mixed polyols (partly absorbed), or 0% for the strictest approach. Net carbs are then multiplied by the servings eaten and by 4 kcal per gram for calories.
- Total
- Total carbohydrate per serving from the label
- s
- Share of sugar alcohols subtracted (1, 0.5 or 0)
Worked examples
Low-carb protein bar (US label)
The bar lists 24 g total carbs including 9 g fiber and 6 g of maltitol. Subtracting all the fiber and half the maltitol (3 g) leaves 24 − 9 − 3 = 12 g net carbs.
Keto ice cream with erythritol, 2 servings
Erythritol is subtracted in full, so each serving has 18 − 6 − 9 = 3 g net carbs. Two servings add 6 g net carbs, or about 24 kcal from carbohydrate.
UK label: 10 g carbohydrate, 5 g fiber
EU and UK labels already exclude fiber from the carbohydrate figure, so the 10 g shown is effectively net carbs. The calculator does not subtract the 5 g of fiber a second time.
Frequently asked questions
How do you calculate net carbs?+
On a US label, take Total Carbohydrate and subtract dietary fiber, then subtract sugar alcohols (all of erythritol, about half of others) and any allulose. What remains is net carbs.
Should I count net carbs or total carbs on keto?+
Most keto plans use net carbs, typically 20–50 g a day, because fiber does not raise blood glucose. Some people with diabetes or stalled progress prefer to count total carbs for a stricter limit.
Why subtract only half of sugar alcohols?+
Sugar alcohols such as maltitol, sorbitol and xylitol are partly absorbed and can raise blood sugar. Erythritol is the exception — about 90% is absorbed and excreted unchanged — so it is usually subtracted in full.
Do I subtract fiber on European labels?+
No. In the EU, UK and Australia, the carbohydrate figure on the label already excludes fiber, so subtracting it again would undercount carbs. Only sugar alcohols (polyols) still need removing.
Is net carbs an official FDA term?+
No. The FDA does not define “net carbs” or “impact carbs”, so manufacturers calculate them differently. Checking the label yourself with a consistent method is more reliable than front-of-pack claims.
This tool gives general estimates and is not medical advice. Talk to a doctor or qualified professional about your health, diet or training.