ketoside

How We Calculate Net Carbs

By Nicolas

Last updated:

A quick health note: This page compares food labels. It isn’t medical advice. If you have diabetes, take glucose-lowering medication, are pregnant or breastfeeding, or manage any medical condition, talk to your doctor or a registered dietitian before you change how you eat.

Net carbs here = total carbohydrate minus fiber, minus allulose and erythritol in full, minus half of other sugar alcohols such as maltitol. Glycerin is not subtracted. “Net carbs” isn’t a term the FDA defines, and the American Diabetes Association recommends counting total carbs, so we show both. See the formula below.

The rest of this page explains each part of that sentence, and why every product table on Ketoside shows total carbs, fiber and the type of sugar alcohol next to our net-carb number.

“Net carbs” isn’t an official number

“Net carbs” has no legal definition. The FDA doesn’t use it, and the American Diabetes Association doesn’t recognize it. The ADA recommends counting total carbohydrate and monitoring your glucose (ADA). How companies calculate a “net carb” figure isn’t standardized, and “keto” and “low-carb” on a package aren’t claims the FDA regulates (ADA Diabetes Food Hub).

That’s why we never present our figure as the official one. We call it ketoside net carbs, show the brand’s own claim beside it as “Label claims X g net”, and explain any gap of 1 g or more.

What’s already inside “Total Carbohydrate”

On a US Nutrition Facts panel, Total Carbohydrate is calculated by difference, so dietary fiber, sugars and sugar alcohols are all already inside it. The sugar-alcohol line is voluntary unless the label makes a claim about sugars or sugar alcohols (21 CFR 101.9). Net carbs means taking some of those parts back out.

Our formula

Per serving, from the US label:

ketoside net carbs = total carbohydrate − fiber − allulose − erythritol − ½ × (maltitol, sorbitol, xylitol, isomalt, lactitol and other sugar alcohols)

We never go below 0 g, and we round to one decimal place. We apply the same formula to every product, whatever the package says.

Fiber

We subtract the dietary fiber line in full. On US labels, fiber includes intrinsic plant fiber plus isolated or added fibers the FDA accepts. Some “modified wheat starch” ingredients (a resistant starch type known as RS4) can be counted as dietary fiber on US labels under FDA policy (FDA). How a given starch affects your own blood sugar may differ, and a label can’t tell you that.

EU and UK labels list fibre separately and don’t include it in “carbohydrate”, which does include polyols (Regulation (EU) No 1169/2011, Annex I), so we never subtract fiber twice. The products on our pages use US labels.

Allulose

We subtract allulose in full when the label gives the amount. Under FDA guidance, allulose doesn’t have to be counted in Total Sugars or Added Sugars on the label, but it is still part of Total Carbohydrate (FDA). If a product contains allulose but the label doesn’t say how much, we don’t guess, and we don’t rank it.

Erythritol

We subtract erythritol in full. The FDA’s calorie factor for erythritol is 0 calories per gram, compared with 1.6 to 3.0 for other sugar alcohols such as maltitol (2.1), xylitol (2.4) and sorbitol (2.6) (21 CFR 101.9). That’s the basis for treating it differently.

Other sugar alcohols: half, as an approximation

For maltitol, sorbitol, xylitol, isomalt and other sugar alcohols, we subtract half. The UCSF Diabetes Teaching Center teaches subtracting half of sugar-alcohol grams, and notes that sugar alcohols still affect blood sugar, though less than sugar (UCSF). The half is a convention, not a measured value for each sugar alcohol or for each person, so treat the result as an approximation.

If a label shows one “Sugar alcohols” line without a breakdown, we subtract it in full only when erythritol is the only sugar alcohol in the ingredients. Otherwise we subtract half.

Glycerin: counted in full

Glycerin (glycerol) is a carbohydrate, and we haven’t found a primary FDA source on how it should be treated in a net-carb count. So we take the conservative route and don’t subtract it. Some brands do subtract it, which is one reason our number can be higher than the one on the package.

When glycerin and sugar alcohols share one line

Some labels lump glycerin and sugar alcohols into a single “Sugar alcohols” line. When that happens, we first look for a breakdown on the brand’s site or a label photo and use it if we find one. If there isn’t one, we subtract half of the line, and the product card carries this note: “Estimate: the label doesn’t split glycerin from other sugar alcohols.” When glycerin and other sugar alcohols share the line, we never subtract the whole line and never subtract none of it. If glycerin is the only sugar alcohol in the ingredients, we don’t subtract any of the line, because glycerin is counted in full.

Rounding and “0 g” labels

Total carbs, fiber, sugars and sugar alcohols are each declared to the nearest gram, and less than 0.5 g may be shown as 0 (21 CFR 101.9). So a product that comes to 0 g net carbs can be slightly above 0, and a gap of up to a gram between our number and the brand’s can come from rounding alone. A “0 g” figure adds up if you eat several servings.

What you’ll see on every product table

  • ketoside net carbs, our figure, in bold.
  • Total carbs, fiber and the type of sugar alcohol (or “none listed”), so you can count total carbs if that’s what you and your care team use.
  • The brand’s claim, shown as “Label claims X g net”, or “no claim”.
  • A note wherever our number and the brand’s differ by 1 g or more, and “(estimate)” where a mixed line forced the half rule.
  • A numbered source for every figure, with the date we checked it.

Where this method is used

Every product table on keto snacks, keto bread, low carb pasta, low carb crackers and low carb bagels uses this formula.

Sources

  1. American Diabetes Association, Get to Know Carbs: https://diabetes.org/food-nutrition/understanding-carbs/get-to-know-carbs
  2. ADA Diabetes Food Hub, Nutrition-Related Claims You Should Know About (): https://diabetesfoodhub.org/blog/nutrition-related-claims-you-should-know-about
  3. 21 CFR 101.9, Nutrition labeling of food (eCFR): https://www.ecfr.gov/current/title-21/chapter-I/subchapter-B/part-101/subpart-A/section-101.9
  4. FDA, Questions and Answers on Dietary Fiber: https://www.fda.gov/food/nutrition-food-labeling-and-critical-foods/questions-and-answers-dietary-fiber
  5. FDA, Guidance for Industry: The Declaration of Allulose and Calories from Allulose on Nutrition and Supplement Facts Labels (Oct 2020): https://www.fda.gov/regulatory-information/search-fda-guidance-documents/guidance-industry-declaration-allulose-and-calories-allulose-nutrition-and-supplement-facts-labels
  6. UCSF Diabetes Teaching Center, Counting Sugar Alcohols: https://diabetesteachingcenter.ucsf.edu/living-diabetes/diet-nutrition/understanding-carbohydrates/counting-sugar-alcohols
  7. Regulation (EU) No 1169/2011, Annex I (food information to consumers): https://www.legislation.gov.uk/eur/2011/1169/annex/I