Counting carbs on keto comes down to one core skill: tracking net carbs and keeping them between 20 and 50 grams per day. Net carbs are the carbohydrates that actually raise your blood sugar, and calculating them is straightforward once you know what to subtract and where hidden carbs tend to lurk.
The Net Carb Formula
The standard calculation is simple: take the total carbohydrates listed on a food label and subtract the grams of dietary fiber. If the product contains sugar alcohols, subtract those too. So a protein bar with 24 grams of total carbs, 8 grams of fiber, and 10 grams of sugar alcohols would come out to 6 net carbs.
The logic behind this subtraction is that fiber passes through your digestive system without significantly raising blood sugar. Your body can’t break it down into glucose the way it processes starches and sugars. Both soluble and insoluble fiber are subtracted equally in net carb math, and both appear to support healthy blood sugar regulation.
Sugar alcohols get subtracted for a similar reason: most of them barely register on the glycemic index. But not all sugar alcohols are created equal, and this matters for your count.
Sugar Alcohols That Actually Matter
Erythritol has a glycemic index of just 1 (compared to 65 for table sugar), making it essentially free to subtract completely. Sorbitol, mannitol, and isomalt all fall in the 2 to 4 range, so they’re also safe to fully deduct.
Maltitol is the outlier. With a glycemic index of 35, it raises blood sugar meaningfully more than other sugar alcohols. Many keto practitioners subtract only half the maltitol grams rather than the full amount. If a “sugar-free” candy bar lists 15 grams of maltitol, counting 7 or 8 of those grams toward your total gives a more accurate picture of the blood sugar impact. Check ingredient lists carefully, because maltitol is one of the most common sugar alcohols in commercial low-carb products.
Xylitol sits in a middle zone with a glycemic index of 12. It’s low enough that most people subtract it fully, but if you’re very strict about staying under 20 net carbs, counting half is a reasonable precaution.
Watch for Allulose on Labels
Allulose is a newer sweetener showing up in keto-friendly products, and it creates a labeling quirk worth understanding. The FDA requires manufacturers to include allulose under “Total Carbohydrate” on the nutrition label because it is technically a carbohydrate. However, allulose contributes only about 0.4 calories per gram (compared to 4 calories per gram for regular sugar) and has virtually no effect on blood sugar.
This means allulose inflates the total carb number on the label even though it shouldn’t count toward your net carbs. You need to check the ingredient list or the line items on the label to spot it. Some brands now print a separate “net carb” callout on the front of the package that already excludes allulose, but the official Nutrition Facts panel will still show a higher total carb number.
How to Read a Nutrition Label
U.S. Nutrition Facts labels break total carbohydrate into three mandatory sub-components: dietary fiber, total sugars, and added sugars. Sugar alcohols may appear as well, but they’re not always listed separately. If a product advertises “sugar-free” or “no sugar added” and the math doesn’t add up (total carbs minus fiber is much higher than total sugars), there are likely sugar alcohols or other sweeteners present. Check the ingredient list to confirm.
Always verify the serving size before you do any math. A bag of cauliflower rice might list 3 net carbs per serving, but the serving might be just half a cup. If you eat the whole bag, you could be looking at four or five times that amount. This sounds obvious, but serving size miscounts are one of the most common carb-tracking errors.
Your Daily Carb Budget
Most ketogenic protocols target less than 50 grams of total carbs per day, and many people start at 20 grams of net carbs to reliably enter ketosis. Harvard’s School of Public Health notes that 20 grams is common for the stricter end and 50 grams is the upper boundary. Nutritional ketosis, the metabolic state where your body primarily burns fat for fuel, is defined as blood ketone levels between 0.5 and 3 mmol/L.
Where you fall in the 20 to 50 gram range depends on your body. Some people stay in ketosis at 40 net carbs; others get knocked out above 25. Starting at 20 grams for the first two to four weeks gives you a reliable baseline. From there, you can gradually increase by 5 grams at a time and monitor how you feel or, if you want precision, test blood ketone levels to find your personal ceiling.
Carb Counts for Common Keto Foods
Vegetables are the backbone of keto nutrition, but their carb content varies more than people expect. One cup of raw broccoli has about 6 grams of total carbs and 2 grams of fiber, giving you 4 net carbs. Cauliflower is slightly lower at about 3 net carbs per cup raw. Spinach is one of the most keto-friendly greens: a cup of raw spinach has roughly 1 gram of total carbs with nearly 1 gram of fiber, making it close to zero net carbs. Cooked spinach is denser, though, with 7 grams total and 4 grams fiber (3 net carbs per cup cooked).
Meat, fish, eggs, butter, and most oils contain zero carbs. Cheese typically has less than 1 gram per ounce. Nuts vary widely: pecans and macadamias are very low, while cashews can add up fast at around 8 net carbs per ounce.
Hidden Carbs That Add Up Fast
Spices and condiments are the sneakiest source of uncounted carbs. Individually they seem negligible, but they accumulate quickly when you’re working with a budget of 20 grams. A tablespoon of paprika has 3.7 grams of carbs. A tablespoon of balsamic vinegar adds 2.7 grams. Even a single teaspoon of garlic powder contributes 2.3 grams, and cinnamon adds 2.1 grams per teaspoon.
If you’re making a spice rub with paprika, garlic powder, onion powder (1.9 grams per teaspoon), and black pepper (1.5 grams per teaspoon), you could easily use 8 to 10 grams of carbs before you’ve even touched a vegetable. This doesn’t mean you need to avoid spices, but you do need to count them. Herbs like basil, oregano, and thyme are lower-carb alternatives when you want flavor without the starchy hit.
Sauces are another common blind spot. Ketchup, barbecue sauce, teriyaki sauce, and honey mustard all pack several grams of sugar per tablespoon. Salad dressings, especially low-fat versions (which replace fat with sugar), can add 3 to 7 grams of carbs per serving. Ranch, blue cheese, and oil-and-vinegar dressings are typically safer options.
Practical Tracking Methods
A food scale paired with a tracking app is the most reliable system, especially in the first few weeks when you’re still learning the carb content of your regular foods. Carb Manager is one of the most widely used keto-specific apps, with a database of over a million foods and automatic net carb calculation that accounts for fiber and sugar alcohols. Cronometer and MyFitnessPal are popular alternatives, though MyFitnessPal doesn’t calculate net carbs by default and requires some manual subtraction.
Weigh and log everything for at least the first two to three weeks. Most people find that after a month of diligent tracking, they develop an intuitive sense for portion sizes and carb counts in their regular meals. At that point, you can shift to logging only new or unfamiliar foods while estimating your staples.
One practical shortcut: build a list of 10 to 15 meals you eat regularly and pre-calculate their net carbs. When 80% of your meals come from a known rotation, daily tracking becomes much less tedious. You only need to calculate from scratch when you try something new or eat out.
Whole Foods vs. Packaged Products
Packaged “keto-friendly” products deserve extra scrutiny. The term “net carbs” on packaging isn’t regulated by the FDA, so manufacturers sometimes subtract ingredients they probably shouldn’t, like maltitol or tapioca fiber (which can raise blood sugar more than other fibers). Compare the total carbohydrate line on the Nutrition Facts panel against the marketed net carb claim, and check what’s being subtracted.
Whole foods make tracking simpler because their carb content is consistent and well-documented. A chicken thigh is always zero carbs. An avocado is always about 3 net carbs. You don’t need to decode ingredient lists or worry about creative label math. The more of your diet that comes from single-ingredient foods, the less mental energy carb counting requires.