A plain baked potato without skin has about 110 calories, according to the Washington State Potato Commission. The potato, a starchy vegetable, contains manly essential nutrients, including potassium. Eating the skin of the potato adds needed fiber but few calories. The flesh of a 6-oz. baked potato contains 110 calories. Topping a baked potato with 1 tbsp. of butter or margarine adds 100 calories. A tablespoon of sour cream adds another 30 calories.