How many carbs are in watermelon?

There are 21 grams of total carbohydrates in one 280 gram serving of raw watermelon. Seventeen grams of these carbohydrates are from the natural sugars found in watermelon. Watermelon also contains 1 gram of fiber per serving.

Although a large proportion of total calories in watermelon come from natural sugars, the fruit is a very good source of vitamins A and C as well as potassium. Watermelon is high on the glycemic index, with a rating of 72. People with diabetes should keep this in mind as watermelon can readily cause a surge in blood-sugar levels with such a high glycemic index rating.