Watermelon is one of the lowest-calorie fruits you can eat. A full cup of diced watermelon has just 46 calories — and it is over 91% water by weight. That makes it one of the best volume foods you can reach for when you want something sweet without blowing your calorie budget.
Watermelon Calories by Serving Size
| Serving | Weight | Calories | Carbs | Sugar |
|---|---|---|---|---|
| 100 grams | 100g | 30 | 7.6g | 6.2g |
| 1 cup, diced | 152g | 46 | 11.5g | 9.4g |
| 1 wedge (1/16 of melon) | 286g | 86 | 21.6g | 17.7g |
| 10 watermelon balls | 122g | 37 | 9.2g | 7.6g |
A standard wedge — the crescent-shaped slice you would get at a cookout — is about 1/16 of a whole melon and comes in at 86 calories. That is less than a single granola bar.
Full Nutrition: 1 Cup Diced Watermelon (152g)
| Nutrient | Amount |
|---|---|
| Calories | 46 kcal |
| Protein | 0.9g |
| Total Fat | 0.2g |
| Carbohydrates | 11.5g |
| Fiber | 0.6g |
| Sugars | 9.4g |
| Vitamin A | 865 IU |
| Vitamin C | 12.3mg |
| Potassium | 170mg |
Source: USDA FoodData Central.
Watermelon vs Other Summer Fruits
How does watermelon stack up against other fruits you would find at a summer barbecue? Per 100 grams:
| Fruit | Calories per 100g | Water Content |
|---|---|---|
| Watermelon | 30 | 91.4% |
| Strawberries | 32 | 90.9% |
| Cantaloupe | 34 | 90.2% |
| Pineapple | 50 | 86.0% |
| Grapes | 69 | 80.5% |
Watermelon wins. It has the fewest calories and the highest water content of any popular summer fruit. You would need to eat more than two cups of watermelon to match the calories in one cup of grapes.
Why Watermelon Is the Ultimate Volume Food
Watermelon is 91.4% water. For every pound you eat, over 14 ounces of it is just water.
This matters for weight loss because water adds weight and volume to food without adding any calories. Your stomach registers fullness based on volume, not calories. So a big bowl of watermelon fills you up the same way a big bowl of pasta would — except the watermelon has a fraction of the calories.
Researchers call this calorie density, and watermelon has one of the lowest at just 0.30 calories per gram. For context, bread is about 2.65 cal/g and nuts are around 5.5 cal/g.
If you are tracking your intake, use our daily calorie calculator to find your target — then see how easy it is to fit watermelon into your day. And since watermelon is mostly water, it counts toward your hydration goals too. Check our water intake calculator to see how much you should be drinking.
Is Watermelon Good for Weight Loss?
Yes. Watermelon is one of the best foods for weight loss, for three simple reasons:
- Extremely low calorie density. At 30 calories per 100g, you can eat a large amount and barely dent your daily budget.
- High water content. The 91% water content means it fills your stomach quickly.
- It satisfies sweet cravings. When you want dessert after dinner, a cup of watermelon at 46 calories beats a bowl of ice cream at 270+.
But what about the glycemic index? You may have heard that watermelon has a high GI (around 72-80). That sounds alarming until you understand what it actually means.
The glycemic index measures how quickly 50 grams of carbohydrate from a food raises blood sugar. To get 50g of carbs from watermelon, you would need to eat about 4.5 cups — over 660 grams. Nobody does that in one sitting.
What matters more is the glycemic load, which accounts for how much you actually eat. One cup of watermelon has a glycemic load of about 5, which is considered low. So despite the high GI number, watermelon does not cause a significant blood sugar spike in real-world portions.
The Watermelon Sugar Myth
A cup of watermelon has 9.4 grams of sugar. That scares some people. It should not.
This is naturally occurring fructose bound up in a food that is 91% water with fiber, vitamins, and antioxidants. It is nothing like the 39 grams of added sugar in a can of Coke.
Your body handles whole fruit sugar differently than added sugar. The water and fiber in watermelon slow digestion and prevent the rapid blood sugar spikes you get from processed sweets. No credible nutrition research has ever shown that eating whole fruit causes weight gain.
For comparison: a medium banana has about 14g of sugar, an apple has 19g. Watermelon is actually on the lower end for fruit sugar — it just gets a bad reputation because of the glycemic index confusion.
How to Use Watermelon in a Calorie Budget
- Post-workout snack: 2 cups of diced watermelon (92 cal) rehydrates you and provides quick carbs for glycogen replenishment.
- Dessert swap: Freeze watermelon cubes for 2 hours. They taste like sorbet for 46 calories a cup.
- Volume hack: Add watermelon to salads with feta and mint — the water content makes the salad feel massive.
- Hydration boost: On hot days, watermelon counts toward your fluid intake.
