A whole watermelon contains approximately 1,360 calories according to the United States Department of Agriculture (USDA)

. Here are some common serving sizes and their calorie content:

• One cup of diced watermelon (about 152 grams) has around 46 calories

• One slice or wedge, which is about 1/16th of a whole melon (around 286 grams), contains about 86 calories

Watermelon is mostly water (over 90%) and low in calories, with most of its calories coming from natural sugars in the form of carbohydrates

. It also provides small amounts of protein and fat. In summary:

• Whole watermelon: ~1,360 calories
• 1 cup diced: ~46 calories
• 1 slice (1/16th melon): ~86 calories

This makes watermelon a low-calorie, hydrating fruit option rich in vitamins and antioxidants.