Watermelon is a low-calorie fruit with the following calorie content depending on the serving size:

• About 30 calories per 100 grams of watermelon

• Approximately 38–39 calories per 100 grams, according to some sources

• Around 46 calories in one cup (about 152 grams) of diced watermelon

• About 86 calories in one slice or wedge (1/16 of a whole watermelon)

• A whole watermelon (about 15 inches long by 7.5 inches diameter) contains roughly 1,360 calories

The variation in calories per 100 grams is minor, but the standard reference is roughly 30 to 46 calories per 100 grams or one cup of watermelon. This low calorie count is mainly due to watermelon being over 90% water, making it a hydrating and low-energy-dense fruit

. In summary, watermelon has about 30 to 46 calories per 100 grams or one cup serving, with a whole melon containing around 1,360 calories in total. This makes it a refreshing, low-calorie option rich in water, vitamins, and minerals