There are 121 calories in 1 large Bananas. Get full nutrition facts and other common serving sizes of Bananas including 1 oz and 1 extra small. 1 large banana (Raw) contains 121 Calories. The macronutrient breakdown is 93% carbs, 3% fat, and 4% protein . This is a good source of potassium (10% of your Daily Value) and vitamin b6 (38% of your Daily Value). Enter a daily calorie target to see a sample of how our generator automatically builds a complete, balanced plan to meet your goals. Learn how much protein is in a banana and how it can benefit your health. Find out how to incorporate bananas into your diet with creative recipes and tips. Potassium: 358 mg Magnesium: 27 mg Nutritional Facts of Banana Almost three-fourths of a banana is water. Specifically, 100 grams of banana contains 75 grams of water. The remaining has 23 per cent carbohydrates and 1 percent protein . The carbohydrate content for a raw banana is constant. In such a case, most of it is starch and very little sugar.