How to use the Net Carbs
- Enter total carbohydrate per serving from the label.
- Subtract dietary fibre.
- Subtract sugar alcohols, halving the figure for maltitol.
- Track the daily total against your 20–50 g target.
How the calculation works
Net carbs = total carbohydrate − fibre − sugar alcohols. Fibre is not absorbed as glucose, so it is subtracted in full. Sugar alcohols vary: erythritol is essentially zero-impact and subtracted fully, while maltitol raises glucose appreciably and is conventionally only half-subtracted. European labels already exclude fibre from the carbohydrate figure, so subtracting it again double-counts.
Nutritional ketosis is generally defined as blood ketones of 0.5–3.0 mmol/L, reached for most people at 20–50 g of net carbs a day within two to four days. A typical macro split is 70–75% of energy from fat, 20–25% from protein and 5–10% from carbohydrate. Protein should not be cut below need — around 1.6 g per kg of lean mass protects muscle, and the old fear of protein disrupting ketosis is largely unfounded at ordinary intakes.
Net carbs = total carbs − fibre − sugar alcohols (maltitol counted at 50%)Source: Nutritional ketosis thresholds and net carb accounting per ketogenic diet clinical literature.
Worked example
A bar with 24 g total carbohydrate, 9 g fibre, 8 g erythritol and 4 g maltitol.
- Subtract fibre: 24 − 9 = 15.
- Subtract erythritol in full: 15 − 8 = 7.
- Subtract half the maltitol: 7 − 2 = 5.
- Net carbs = 5 g.
5 g net carbs — a quarter of a 20 g daily budget from one bar.
Frequently asked questions
How many net carbs for ketosis?+
Usually 20–50 g a day. Lower is more reliable; activity level and individual tolerance shift the threshold.
Do all sugar alcohols count the same?+
No. Erythritol is near zero-impact; maltitol raises glucose meaningfully and is half-counted.
How long to enter ketosis?+
Typically two to four days of consistent restriction, faster with exercise and an overnight fast.
Should I subtract fibre on EU labels?+
No. European labels already exclude fibre from the carbohydrate value.
Last reviewed August 31, 2026. We review this page whenever the underlying formula, tax year, published rate or standard changes.