Reducing carbs in your diet can help promote more stable blood glucose levels and, in turn, support metabolic health. However, not all carbs are the same. The body processes sugars, sugar alcohols, starches, and fibers differently, meaning each type of carb affects blood sugar differently.
Calculating net carbs is one tactic to understand better how a specific food may affect your blood glucose. While you may have heard the term “net carbs” or seen it on packaged foods, you may not know what it means or how to use this number to your advantage.
Here we’ll explain everything you need to know about net carbs, including whether keeping tabs on your intake might help you reach your metabolic health goals.
What Are Net Carbs and How Do You Calculate Them?
First, it’s important to note that “net carbs” is not a clinical or FDA-sanctioned definition. Anytime you see “net carbs” (or “impact carbs” or “digestible carbs”) on a food package, it’s marketing language invented by the food industry, primarily to appeal to low-carb and keto dieters.
To calculate net carbs, you subtract the grams of fiber, erythritol, and allulose, and half the grams of other sugar alcohols (e.g. xylitol) from the total carb content. For whole or minimally processed foods without these added sweeteners, you’d simply subtract the fiber from the total carb content. That is:
Total carbs – fiber – allulose – erythritol –½(other sugar alcohols) = Net carbs
This formula is used because, unlike other carbs, fiber, and sugar alcohols (which some researchers call “indigestible sugars”) don’t break down into glucose during digestion. Therefore, your body can’t use them for energy, and they are unlikely to cause a blood sugar rise.
Note that the nutrition facts label doesn’t list net carbs because, again, the FDA (which regulates the label) doesn’t use net carbs as a metric. That means the number you see on the package could be inaccurate, so use the info on the nutrition facts label and do the math yourself.
Is “Net Carbs” a Useful Metric?
The key point to know is that the standard formula weighs fiber and sugar alcohols equally even though they have very different effects on your body. Fiber is critical to optimal metabolic health, but sugar alcohols have little to no nutritional value.
Fiber helps maintain a healthy balance in the gut microbiome by feeding “good” bacteria (i.e., probiotics), which then produce short-chain fatty acids that have anti-inflammatory effects and have been connected with improved insulin sensitivity. Fiber also takes longer to digest than other carbs, which means a slower rate of glucose entering the bloodstream and thus a lower glucose response to a meal. There is strong evidence that high-fiber diets (in most studies, 30 to 40 grams per day) can reduce insulin resistance and the risk of Type 2 diabetes by 20-30%.
On the other hand, sugar alcohols—such as xylitol, sorbitol, mannitol, maltitol, isomalt, lactitol, and erythritol—have few health benefits.
These hybrid carbohydrates contain a combination of sugar and alcohol molecules. Manufacturers like to use sugar alcohols because they mimic the taste of natural sugar for fewer calories and they have a low glycemic index, meaning they’re unlikely to cause blood sugar spikes.
Although generally well-tolerated in moderation (about 10 to 15 grams a day), high consumption of sugar alcohols can cause digestive issues such as diarrhea and bloating. Plus, most foods that contain sugar alcohols are processed. These foods tend to lack fiber and other beneficial nutrients and are linked with higher risk of everything from cardiovascular disease to Type 2 diabetes.
Bottom line: As much as possible, favor whole and minimally processed foods over ultra-processed foods. And when choosing packaged goods, look for the most fiber and lowest overall carb count.
How You Can Apply Net Carbs?
Calculating net carbs with a focus on fiber can help you identify which carb-containing foods are least likely to spike blood sugar. Although it’s possible to calculate net carbs for whole foods, this tactic is most useful when picking out packaged foods, such as tortillas, grain-free granolas, frozen meals, and ice cream. Knowing how to do the math will help you vet potentially inaccurate marketing claims on food labels and choose the best options for your health goals.
Here are some examples of net carb content of common foods:
However, keep in mind that we rarely eat foods like tortillas alone. When you add protein, fats, vegetables, and other ingredients, the total net carbs of a meal changes. For example, a wrap that contains avocado and lean ground turkey will have more protein and fiber. And that number is what matters. Plus, eating a balance of protein, fiber, and healthy fats in combination with carbohydrates slows digestion, promoting more steady and smaller rises in blood sugar.
When tracking carbs, 20 to 75 grams of net carbs per day is a good benchmark, according to Stephanie Greunke, a dietitian, trainer, and Whole30 advisor. “Men can often get away with lower levels of net carbs, while women may need closer to 50 to 100 grams of net carbs or more to support their reproductive cycle and overall hormonal health,” she adds.
If you’re on a keto diet, however, most plans allow for a maximum of 50 grams of total carbohydrates per day to stay in ketosis. In that case, packaged foods should have 4–15 grams of net carbs per serving.
The only people who should avoid relying on net carbs are those living with diabetes. The American Diabetes Association recommends tracking total carbs instead of net carbs out of caution, because sometimes fiber or sugar alcohols may be partially metabolized and potentially impact blood sugar. If you have diabetes, work with your doctor to closely manage your glucose levels and carbohydrate intake.