Butter is extremely low in carbohydrates. One tablespoon contains just 0.01 grams of carbs, making it effectively a zero-carb food. The remaining calories come almost entirely from fat, with 11.52 grams per tablespoon and a trace amount of protein at 0.12 grams.
Why Butter Has Almost No Carbs
Butter is made by churning cream until the fat separates from the liquid (buttermilk). That process removes nearly all the milk sugar, or lactose, which is the main carbohydrate in dairy. What’s left is almost pure milk fat. This is also why butter is better tolerated than milk by people who are sensitive to lactose.
Because butter contains so little carbohydrate, it doesn’t even register on the glycemic index. Foods like meat and butter are excluded from GI charts entirely since they have no meaningful effect on blood sugar.
Butter on Keto and Low-Carb Diets
Butter is a staple in ketogenic eating for good reason. A standard keto diet calls for 70 to 80 percent of daily calories from fat, with carbohydrates limited to less than 50 grams a day and sometimes as low as 20 grams. At 0.01 grams of carbs per tablespoon, you could eat several tablespoons of butter without making a dent in your daily carb limit.
That said, butter is calorie-dense. A single tablespoon packs around 100 calories, nearly all from fat. If you’re using a low-carb diet for weight loss, the total calories still matter. Cooking with a tablespoon or two is fine, but adding butter liberally to every meal can push your calorie intake higher than you realize. Tracking portions for the first few weeks helps build an intuitive sense of how much you’re actually using.
Grass-Fed vs. Regular Butter
From a carb standpoint, there’s no difference between grass-fed and conventional butter. Both are essentially zero carb. The differences show up in the fat composition. Grass-fed butter contains higher levels of omega-3 fatty acids and a group of fatty acids called CLA, which may support heart health. It also has a slightly higher proportion of unsaturated fat compared to regular butter. These differences are modest per serving, but they add up if butter is a regular part of your diet.
Grass-fed butter typically has a deeper yellow color, which comes from the beta-carotene in the grass the cows eat. Nutritionally, either type works on a low-carb plan.
Ghee and Clarified Butter
Ghee takes butter one step further by cooking off the water and milk solids. The result is pure butterfat with zero carbs, zero lactose, and a higher smoke point for cooking. If you’re strictly limiting carbs or avoiding all dairy proteins, ghee is the cleanest option. It has a slightly nuttier flavor and stores longer at room temperature than regular butter.
What About Flavored and Whipped Butters
Plain butter is reliably zero carb, but flavored varieties can be different. Honey butter, for example, adds several grams of sugar per serving. Garlic butter and herb butter usually stay very low carb, but store-bought versions sometimes include fillers or sweeteners. Checking the label takes a few seconds and can save you from unexpected carbs.
Whipped butter has the same carb content as regular butter per gram, but because air is whipped in, a tablespoon of whipped butter contains less actual butter. This means fewer calories and less fat per scoop, which can be useful if you’re watching portions.
Margarine and Butter Substitutes
Most margarines and butter-like spreads are also very low in carbs, typically under 0.5 grams per tablespoon. However, their fat profiles differ significantly from butter. Many contain vegetable oils that are higher in omega-6 fatty acids, and some older formulations included trans fats (though this has become less common). If you’re choosing between butter and margarine purely for a low-carb diet, both work. The decision comes down to the type of fat you prefer and how you feel about processed versus whole-food options.
The Saturated Fat Question
Butter is high in saturated fat, which has been a point of debate in nutrition science for decades. Traditional guidelines recommend limiting saturated fat, even on low-carb diets, by favoring sources like olive oil, avocados, and nuts. Some researchers have pushed back on this, arguing that restricting saturated fat on a carbohydrate-restricted diet is unnecessary and may reduce some of the metabolic benefits of carb reduction. The science is genuinely unsettled on this point. A practical middle ground is using butter as one of several fat sources rather than your only one, mixing in olive oil, avocado, fatty fish, and nuts for variety.