To find net carbs, subtract fiber and sugar alcohols from the total carbohydrates listed on a nutrition label. The basic formula is: total carbs minus fiber minus sugar alcohols equals net carbs. This number represents the carbohydrates your body actually digests and converts to blood sugar, which is why it matters for blood sugar management and low-carb diets.
The Net Carb Formula
Start with the “Total Carbohydrate” line on a U.S. nutrition label. Fiber and sugar alcohols are both listed as sub-categories underneath it, indented below the total. Subtract both from the total to get your net carbs.
For example, if a protein bar lists 25 grams of total carbohydrates, 8 grams of fiber, and 10 grams of sugar alcohols, the net carbs are 25 minus 8 minus 10, which equals 7 grams.
For whole foods without a label (an apple, a handful of almonds), you can look up the total carbohydrates and fiber in a nutrition database or app and do the same subtraction. Most whole foods don’t contain sugar alcohols, so you’re just subtracting fiber.
Why Fiber Gets Subtracted
Fiber is technically a carbohydrate, but your body can’t break it down into glucose the way it breaks down starches and sugars. It passes through your digestive system largely intact. Because it never enters your bloodstream as sugar, it doesn’t raise blood glucose or trigger an insulin response the way digestible carbs do. That’s why nutrition researchers describe net carbs as the “available carbohydrates” in a food, meaning only the portion your body can actually absorb and use for energy.
This distinction matters most if you’re tracking carbs for blood sugar control or ketosis. Counting fiber against your carb budget would make high-fiber vegetables and nuts look far worse than they actually are in terms of metabolic impact.
Sugar Alcohols: Not All Are Equal
Sugar alcohols are sweeteners commonly found in “sugar-free” or “low-carb” packaged foods. They taste sweet but are only partially absorbed, which is why they’re subtracted from total carbs. Common ones include erythritol, xylitol, sorbitol, and maltitol.
Here’s the catch: not all sugar alcohols behave the same way in your body. Erythritol has a glycemic index of zero, meaning it has virtually no effect on blood sugar. You can subtract it entirely. Xylitol, sorbitol, and isomalt also have minimal blood sugar impact and are generally fine to fully subtract.
Maltitol is the exception worth knowing about. It has a glycemic index as high as 52 (table sugar is 65), which means it raises blood sugar noticeably more than other sugar alcohols. If a product is sweetened with maltitol, subtracting the full amount gives you an artificially low net carb count. A more accurate approach is to subtract only half the maltitol grams. Check the ingredient list, not just the nutrition panel, to see which sugar alcohol a product actually uses.
The Allulose Exception
Allulose is a newer sweetener showing up in low-carb products. It’s technically classified as a sugar, but your body barely absorbs it. The FDA has advised manufacturers that allulose can be excluded from “Total Sugars” and “Added Sugars” on labels, and it’s counted at only 0.4 calories per gram instead of the usual 4. Some manufacturers have petitioned to exclude it from “Total Carbohydrate” entirely, but labeling rules are still catching up.
In practice, this means allulose might or might not be included in the total carbohydrate number on a given product. If it is included, you can subtract it when calculating net carbs, just as you would fiber or erythritol. Look at the ingredient list and any footnotes on the label to figure out how a specific product handles it.
Putting It Into Practice With Whole Foods
Net carb counting is most useful when it changes how you think about a food. A medium avocado is a perfect example: it contains about 13 grams of total carbohydrates, but 10 of those grams are fiber. That leaves only 3 grams of net carbs, making avocado one of the most low-carb-friendly fruits you can eat.
Here’s how a few other common foods break down:
- Raspberries (1 cup): About 15 grams total carbs, 8 grams fiber, so roughly 7 grams net carbs.
- Almonds (1 oz, about 23 nuts): About 6 grams total carbs, 3.5 grams fiber, so roughly 2.5 grams net carbs.
- Broccoli (1 cup chopped): About 6 grams total carbs, 2.4 grams fiber, so roughly 3.6 grams net carbs.
Foods like these look much more accessible once you account for fiber, which is one reason net carb counting encourages eating more vegetables and high-fiber foods rather than avoiding them.
Net Carbs on Keto and Low-Carb Diets
Most people searching for net carbs are following or considering a ketogenic or low-carb diet. A standard ketogenic diet typically limits total carbohydrate intake to less than 50 grams per day, and many people aim for 20 to 30 grams. These targets are almost always stated in net carbs, not total carbs.
That distinction makes a real difference in what your plate looks like. If you’re aiming for 20 grams of net carbs, you can fit in a couple of cups of non-starchy vegetables, some berries, and a handful of nuts without coming close to your limit. If you counted total carbs instead, those same foods would eat up your budget much faster, potentially pushing you toward a less nutritious, more restrictive version of the diet.
Common Label-Reading Mistakes
One frequent error is double-subtracting. Fiber and sugar alcohols are already included in the total carbohydrate number on U.S. labels. You subtract them from the total. You don’t subtract them and then also subtract the sugars listed on the label, because sugars are a separate sub-category that doesn’t overlap with fiber.
Another mistake involves international labels. In many countries (the UK, Australia, most of the EU), nutrition labels already list “Carbohydrates” as the digestible amount with fiber separated into its own line. If you’re reading a European label, the carbohydrate number is already close to net carbs. Subtracting fiber again would undercount.
Finally, be cautious with packaged “low-carb” products that prominently display a net carb count on the front of the package. Manufacturers sometimes use generous math, fully subtracting maltitol or counting certain fibers that may still have a modest blood sugar effect. Your safest bet is to do the calculation yourself from the nutrition facts panel and ingredient list rather than trusting a marketing claim.