How Many Calories Are In A Watermelon? | Low-Calorie Facts

Picture a hot afternoon where you slice open a watermelon and the sweet aroma fills the air. Most people assume something this refreshing and sweet must be loaded with calories, but that assumption misses the real story. Watermelon is mostly water — about 92 percent — which naturally keeps the calorie count surprisingly low.

This article breaks down exactly how many calories you will find in a single cup, a standard wedge, and a whole melon. It also covers the macronutrient profile, vitamins, and how watermelon compares to other common fruits so you can fit it into your eating plan with confidence.

Calorie Count by Serving Size

The most straightforward answer depends on how much you are eating. One cup of diced watermelon (152 grams) provides about 46 calories according to USDA data. That same USDA source notes that the standard serving size for nutrition labeling is exactly one cup of diced fruit.

A single wedge or slice — roughly one-sixteenth of a whole melon — comes in at around 86 calories. Two cups of diced watermelon (about 280 grams) totals roughly 80 calories. For the whole melon, the math adds up to approximately 1,360 calories for an average-sized watermelon, though actual weight varies by variety and growing conditions.

Why The Low-Calorie Reputation Sticks

Watermelon earns its reputation as a diet-friendly fruit because of its water content and volume. Most people can eat a generous bowl and still stay within a calorie budget, which feels counterintuitive for something so sweet. The confusion usually comes from the sugar content — watermelon does contain natural sugar, but the water dilutes the calorie density significantly.

• Water content: At 92 percent water, watermelon ranks among the most hydrating fruits. Mayo Clinic notes this high water content is a key reason it remains low in calories by volume.
• Sugar perception: One cup has about 9.4 grams of sugar, but the water and fiber (0.6 grams per cup) help with satiety compared to sugary beverages.
• Volume eating: You can eat two full cups of watermelon for roughly 80 calories — the same calorie cost as about ten almonds or half a banana.
• Carb profile: With only 7.5 grams of carbs per 100 grams, watermelon is the lowest-carb fruit by far according to WebMD comparisons of low-carb fruit options.
• Glycemic load: Despite having a moderate glycemic index, the glycemic load of watermelon is low because the carbohydrate content per serving is relatively small.

These factors together explain why watermelon feels satisfying without tipping the calorie scale. It is not a zero-calorie food, but it is about as close as whole fruits get.

What You Get Beyond The Calorie Count

The calorie number only tells part of the story. One cup of watermelon delivers 12.3 milligrams of vitamin C — about 14 percent of the Daily Value — plus 865 IU of vitamin A from beta carotene. The USDA nutrition facts sheet notes that two cups also provide roughly 6 percent of the Daily Value for potassium and 6 percent for magnesium. You can check the full USDA profile in the 46 calories per cup resource.

Watermelon also contains small amounts of calcium (5 mg per cup), iron (0.2 mg per cup), and sodium (1.5 mg per cup). The beta carotene content (about 0.9 mg in two cups) acts as an antioxidant phytonutrient that supports eye health and immune function, though the amounts are modest compared to orange vegetables like carrots.

Nutrient	Per 1 Cup Diced (152g)	% Daily Value
Calories	46	—
Carbohydrates	11.5 g	4%
Sugar	9.4 g	—
Fiber	0.6 g	2%
Protein	0.9 g	2%
Fat	0.2 g	<1%
Vitamin C	12.3 mg	14%
Vitamin A	865 IU	17%

This table shows that watermelon is primarily a source of carbohydrates in the form of natural sugar, along with meaningful amounts of vitamins A and C. The fat and protein content are negligible, which keeps the total calorie density very low.

How To Fit Watermelon Into Your Day

Watermelon works well in many eating patterns because its calorie load is easy to adjust. You can use serving size to control exactly how many calories you add to a meal or snack. Here are a few practical approaches.

1. Start with one cup as a base serving: At 46 calories, one cup fits easily into any meal plan and provides a satisfying volume of food. Add a small handful of nuts or a dollop of yogurt to make it more balanced.
2. Use it for post-workout hydration: The high water content plus natural sugar can help replenish fluids and glycogen after exercise. A two-cup serving (80 calories) provides about 25 percent of your daily vitamin C needs.
3. Swap higher-calorie desserts: Replace a 200-calorie bowl of ice cream with three cups of watermelon (about 140 calories) and save 60 calories while increasing your vitamin and water intake.
4. Pair it with protein for satiety: Watermelon alone digests quickly, so pairing a one-cup serving with cottage cheese, grilled chicken, or a hard-boiled egg helps keep you full longer.
5. Freeze it for a cold treat: Frozen watermelon chunks or puree can replace sugary popsicles or sorbet with no added sugar, cutting calories by 50 to 100 per serving compared to store-bought options.

These strategies let you enjoy watermelon throughout the summer without guessing whether it fits your goals. The key is portion awareness rather than avoidance.

How Watermelon Compares To Other Fruits

Watermelon sits at the low end of the fruit calorie spectrum, but the differences matter for meal planning. A cup of diced watermelon (46 calories) contains less than half the calories of a medium banana (105 calories) and about one-third the calories of a cup of grapes (100 calories). NC State Extension provides a full watermelon macronutrient breakdown that confirms 11.5 grams of carbohydrates and 0.9 grams of protein per cup.

The sugar content is also lower than many assume. One cup of watermelon has 9.4 grams of sugar, compared to about 16 grams in a cup of grapes and 14 grams in a cup of mango. The fiber content is modest at 0.6 grams per cup, which is lower than berries or apples but consistent with other high-water fruits like cantaloupe.

Fruit (1 cup diced)	Calories	Carbs (g)
Watermelon	46	11.5
Cantaloupe	55	13
Strawberries	50	12
Grapes	100	27
Mango	100	25

This quick comparison shows watermelon consistently ranks lowest or near-lowest in both calories and carbohydrates among common fruits. That makes it a useful choice for anyone watching their sugar or calorie intake while still wanting a sweet, satisfying fruit option.

The Bottom Line

Watermelon delivers around 46 calories per cup, about 86 calories per wedge, and roughly 1,360 calories for an entire melon. It is one of the most water-rich and least calorie-dense fruits available, and its vitamin C and A content add real nutritional value. Portion size remains the main lever — you can enjoy a generous bowl or a small cube and know exactly what you are getting.

For personalized advice on how watermelon fits your specific calorie goals, a registered dietitian or your primary care provider can help match serving sizes to your activity level and overall eating pattern. The USDA also publishes free, searchable nutrition data for all fruits if you want to compare options for your own meal planning.