Learn how many calories , carbs, fats, proteins, vitamins, and minerals are in watermelon . Find out how watermelon can help you fight dehydration, lower blood pressure, and more. There are 45 calories in 150 grams of Watermelon . Get full nutrition facts and other common serving sizes of Watermelon including 100 g and 10 balls. Nutritional information watermelon , fresh View the most important nutritional values of watermelon , fresh. The overview shows the amounts of kcal, proteins, fats, carbohydrates, vitamins and minerals. The default values for watermelon , fresh are shown in 100 grams. You can also enter a different value between 1 and 500 grams to have the nutritional value calculated. You can do this by moving the slider. A portion of watermelon , fresh corresponds to 150 grams. Watermelon is a low-calorie fruit that provides vitamin C, potassium, copper, and citrulline. It may help lower blood pressure, improve insulin sensitivity, and reduce muscle soreness after exercise.