Net carbs are the carbohydrates that actually impact blood sugar. The basic formula is: Net Carbs = Total Carbs − Fiber (and sometimes sugar alcohols).
In other words, net carbs are the carbs your body actually absorbs and uses for energy. Fiber passes through your digestive system without being broken down into glucose, which is why it gets subtracted from the total carb count.
When you eat carbohydrates, your body breaks them down into glucose (blood sugar). This triggers an insulin response, which helps shuttle glucose into cells for energy or storage. However, not all carbs affect blood sugar equally.
Fiber is a type of carbohydrate that your body can't digest. It moves through your digestive tract largely intact, feeding beneficial gut bacteria and promoting digestive health, but it never converts to glucose. That's why subtracting fiber gives you a more accurate picture of the carbs that will actually affect ketosis.
Fiber isn't digested into glucose, so it doesn't spike blood sugar or trigger insulin release. This means you can eat more fiber‑rich vegetables—like spinach, broccoli, and cauliflower—while staying in ketosis.
There are two types of fiber: soluble and insoluble. Soluble fiber dissolves in water and forms a gel-like substance that can help lower cholesterol and regulate blood sugar. Insoluble fiber doesn't dissolve and helps move food through your digestive system. Neither type raises blood glucose levels.
This is great news for keto dieters because it means you can load up on leafy greens, cruciferous vegetables, and other fiber-rich foods without worrying about your carb count. You get all the micronutrients and digestive benefits without the blood sugar impact.
Step 1: Find the total carbohydrates on the nutrition label (usually listed as "Total Carbohydrate")
Step 2: Find the dietary fiber amount (listed under Total Carbohydrate)
Step 3: Subtract fiber from total carbs: Net Carbs = Total Carbs - Fiber
Step 4: If sugar alcohols are present, subtract those too (with some caveats—see below)
That's it. Simple math, powerful results. Once you do this a few times, it becomes second nature.
Example 1: Avocado
Avocado has 8.5g total carbs and 6.7g fiber per 100g.
Net carbs = 8.5g - 6.7g = 1.8g net carbs
This is why avocados are a keto superfood—they're high in healthy fats, filling, and extremely low in net carbs.
Example 2: Broccoli
100g of raw broccoli has 6.6g total carbs and 2.6g fiber.
Net carbs = 6.6g - 2.6g = 4g net carbs
Broccoli is keto-friendly and nutrient-dense, making it a staple vegetable.
Example 3: White Bread (for comparison)
100g of white bread has ~49g total carbs and only ~2.7g fiber.
Net carbs = 49g - 2.7g = 46.3g net carbs
This is why bread kicks you out of ketosis fast—it's almost pure starch with minimal fiber.
Example 4: Spinach
100g of raw spinach has 3.6g total carbs and 2.2g fiber.
Net carbs = 3.6g - 2.2g = 1.4g net carbs
You could eat an entire bag of spinach and barely make a dent in your daily carb limit.
Sugar alcohols (also called polyols) are sweeteners that have fewer calories than sugar and a lower glycemic impact. Common ones include erythritol, xylitol, maltitol, and sorbitol.
Erythritol is the gold standard—it has zero glycemic impact and is usually subtracted 100% from total carbs. If you see erythritol on a label, it's safe to subtract it completely. Most keto desserts and protein bars use erythritol for this reason.
Xylitol has a low glycemic index (GI of 7 vs. sugar's 60-70), but it's not zero. Count about 25-30% of xylitol grams as net carbs to be safe.
Maltitol is the worst offender. It has about 50% the glycemic impact of sugar, which means it can spike blood sugar and kick you out of ketosis. If a product has maltitol, count 50% of those grams as net carbs.
Sorbitol and mannitol are in the middle—count about 50% to be conservative.
If a product contains multiple sugar alcohols, check which ones they are. A protein bar sweetened with erythritol is better for keto than one sweetened with maltitol.
Most people aim for 20–50g net carbs per day to stay in ketosis. If you counted total carbs instead of net carbs, you'd be unnecessarily restricting nutrient-dense vegetables.
For example, a typical keto day might include:
• 2 cups spinach (2g net carbs)
• 1 avocado (3g net carbs)
• 1 cup broccoli (4g net carbs)
• 100g cauliflower rice (3g net carbs)
• A few raspberries (5g net carbs)
Total: 17g net carbs
If you counted total carbs, that same day would be 35-40g, making it seem like you're way over your limit. But in reality, all that fiber isn't affecting your blood sugar or ketosis at all.
This flexibility is what makes keto sustainable long-term. You're not starving or restricting vegetables—you're eating real food and feeling full.
For most people doing keto or low-carb, net carbs are the way to go. It's more flexible, sustainable, and allows you to eat more vegetables.
However, some people prefer tracking total carbs because it's simpler and eliminates any guesswork around sugar alcohols. If you're extremely sensitive to carbs or have hit a plateau, you might experiment with total carbs for a week to see if it makes a difference.
That said, tracking net carbs is the standard approach in the keto community, and it's what we recommend for beginners. It's how the science works, and it's how your body responds.
Mistake 1: Not reading labels carefully
Some labels list "Total Carbohydrate" with fiber already subtracted, while others list it separately. Always check the breakdown. If you see "Net Carbs" on the label, verify it by doing the math yourself.
Mistake 2: Assuming all sugar alcohols are the same
Erythritol is keto-friendly. Maltitol is not. Know the difference. When in doubt, Google the specific sugar alcohol and its glycemic index.
Mistake 3: Forgetting about portion sizes
A food might be low-carb per 100g, but if you eat 300g, the carbs add up fast. Always calculate based on what you actually eat, not the serving size on the label.
Mistake 4: Eating "keto" products without checking the label
Just because something says "keto-friendly" doesn't mean it's actually low in net carbs. Marketing can be misleading. Always verify the numbers yourself.
Mistake 5: Not tracking vegetables
Yes, vegetables are healthy. But if you eat a pound of bell peppers, that's still 15g net carbs. Track everything, at least until you know your staple foods by heart.
Step 1: Set your daily net carb limit
Start with 20-25g net carbs per day if you're new to keto. This virtually guarantees ketosis within 2-3 days. Once you're adapted (4-6 weeks in), you can experiment with 30-40g if you want more flexibility.
Step 2: Prioritize whole foods
Meat, fish, eggs, leafy greens, and healthy fats should make up 90% of your diet. These are naturally low in net carbs and don't require guesswork.
Step 3: Track your intake
Use our calculator or a tracking app to log your net carbs. After a few weeks, you'll memorize the carb counts of your staple foods and won't need to track as obsessively.
Step 4: Test and adjust
Some people can stay in ketosis at 40-50g net carbs per day, especially if they're active. Use ketone strips or a blood meter to find your personal threshold.
• Prioritize whole foods over packaged "keto" products—real food is always better
• Track net carbs for packaged foods, not just total carbs—read every label like a detective
• If progress stalls, lower net carbs by 5-10g for a week and see what happens
• Don't fear vegetables—the fiber doesn't count, so load up on greens
• Stay hydrated and get electrolytes—keto flushes water and sodium, so salt your food
• Give it time—your body needs 2-3 weeks to become fat-adapted
Q: Do I need to count net carbs from vegetables?
A: Yes, but most non-starchy vegetables are so low in net carbs that you can eat them freely. A huge salad with 4 cups of greens might only have 3-4g net carbs.
Q: What about fruit?
A: Most fruits are high in net carbs and should be limited on keto. Berries (strawberries, raspberries, blackberries) are the exception—they're relatively low-carb and high in fiber. Stick to small portions.
Q: Can I eat as much fiber as I want?
A: Yes, fiber doesn't count toward your net carb limit. However, drastically increasing fiber too quickly can cause digestive discomfort (bloating, gas). Ramp up gradually over a week or two.
Q: What if a label doesn't list fiber?
A: If fiber isn't listed, assume there is none and count all carbs as net carbs. This is rare for whole foods but can happen with highly processed items.
Q: Do I subtract fiber from vegetables cooked vs. raw?
A: The fiber content doesn't change when you cook vegetables. What changes is the weight (water evaporates). Always use the nutrition data for the form you're actually eating (raw vs. cooked).
Q: Is 30g net carbs too much for ketosis?
A: It depends on the person. Some people can stay in ketosis at 40-50g net carbs, while others need to stay below 20g. Start strict (20g), then experiment once you're adapted.
Net carbs give you a more accurate picture of how food affects your blood sugar and ketosis. By subtracting fiber (and certain sugar alcohols), you can eat more nutrient-dense vegetables without sabotaging your progress.
The formula is simple: Total Carbs - Fiber = Net Carbs. Master this, track your intake, and you'll have the foundation for long-term keto success.
Don't overthink it. Read labels, subtract fiber, and prioritize whole foods. That's 90% of the work. The rest is consistency.
Use our calculator to get instant net carb data for hundreds of foods. Stay on track, stay consistent, and let the results speak for themselves.