How Much Calories Are in One Slice of Watermelon? Exact Numbers

To put a number on the calories in one slice of watermelon, start with the standard wedge: a 286-gram cut from a halved melon delivers roughly 85 to 90 calories, while a smaller 100-gram triangle runs near 30 calories and a 152-gram cup of diced fruit sits at about 46 calories. Because the fruit is about 92% water by weight, even a generous portion adds only a modest bump to a daily energy budget.

This practical walkthrough breaks down what qualifies as a single slice, compares calories across wedge, diced, and cup servings, and explains why watermelon stays light on the scale despite its sugary taste.

What Counts as a Single Slice of Watermelon

A whole Citrullus lanatus melon can range from 6.8 to 15.9 kilograms, so “one slice” depends entirely on how you cut it. The most common nutrition-database reference is a wedge taken from a halved melon, about 1/16 of the whole fruit, and that wedge typically weighs 286 grams. The weight can climb quickly if you cut thicker pieces or leave extra white rind attached, since the rind itself carries almost no energy but adds grams that show up on a scale.

Smaller triangular cuts from a quartered melon can weigh as little as 100 grams, especially after the rind is trimmed away. Many people default to a cup measurement, and one cup of diced watermelon clocks in at 152 grams. USDA FoodData Central uses that cup figure as the standard serving on nutrition labels, which is why MyFitnessPal and Cronometer log watermelon that way by default. Because trackers and labels lean on the cup reference, you can use a kitchen scale to confirm whether your slice lines up with the 152-gram cup or the 286-gram wedge in any database entry.

Common slice weights at a glance

Those weights shift with variety and ripeness, but they give you a reliable starting point. Cutting thicker wedges or including more of the white rind pushes the weight up, and so do the calories, though only modestly because the rind itself adds almost no energy to the total.

The Calorie Count Across Common Serving Sizes

Calorie density is where watermelon stands out from nearly every other fruit in the produce aisle. At roughly 0.30 calories per gram, it sits far below banana at 0.89 cal/g or grapes at 0.67 cal/g, and that single number does more work than any label reading. A 286-gram wedge delivers about 86 calories, a 100-gram triangle lands near 30 calories, and a standard cup of diced fruit sits at 46 calories, none of which will disrupt a daily intake target.

Because the fruit carries so much water and so little energy per gram, you can eat a surprising amount before the numbers add up. Two cups at 304 grams still come in around 92 calories, which is roughly the calorie cost of a single medium apple. That ratio of volume to energy is the real reason watermelon shows up on almost every low-calorie snack list worth trusting.

How the math scales with portion size

• ▸Half a cup (76 g): About 23 calories, a light add-on to yogurt or cottage cheese.
• ▸One cup (152 g): Around 46 calories, the standard tracker reference and a satisfying snack portion.
• ▸Two cups (304 g): Roughly 92 calories, enough to feel like a meal’s worth of volume.
• ▸Half a whole melon: Can exceed 600 calories, a reminder that volume still adds up.

Because the energy density is so low, you can eat a large volume before the calories become significant. That single fact is what makes the fruit useful for satiety, especially on days when you’re trying to stretch a calorie target across several meals and need something that fills the plate.

Why Watermelon Stays Low in Calories Despite Its Sweetness

Watermelon tastes like candy, yet the sweetness rides on a wave of water carrying a small sugar payload. Roughly 92% of the fruit is water, and the remaining 8% holds the carbohydrates, fiber, and trace nutrients. That water mass dilutes the caloric load so effectively that even a juicy, fully ripe wedge barely registers against a daily intake.

Nearly every calorie in watermelon comes from natural sugars, primarily fructose, glucose, and sucrose. Fat content is essentially zero, and protein sits at roughly 1 gram per cup. The carbohydrate total for a 286-gram slice lands near 22 grams, with sugars making up the bulk of that figure, and dietary fiber contributing about 0.6 to 1 gram of the remainder.

The glycemic index paradox

A glycemic index of roughly 72 places watermelon in the higher range of the standard scale, so its natural sugars tend to reach the bloodstream fairly fast after digestion begins. But the glycemic index only tells you how fast carbs hit your blood, not how many carbs sit in a typical portion. A 152-gram cup has just 11 grams of available carbohydrates, a small enough load that the blood-sugar spike stays modest for most people.

Pairing watermelon with a protein source, like Greek yogurt or a small handful of almonds, slows that absorption further. Combining carbohydrate-rich foods with protein or fat helps blunt post-meal glucose responses, a useful principle when you’re eating fruit on its own, and one that aligns with broader guidance on balanced meals.

That pairing effect raises a broader question about what else watermelon delivers beyond simple sugars.

A Full Nutritional Profile Per Slice

Calories tell only part of the story. A 286-gram wedge of watermelon delivers around 22 grams of carbohydrates, 0.6 to 1 gram of dietary fiber, and a meaningful dose of vitamin C at roughly 21 milligrams, or about 23% of the daily value. That same wedge also supplies a surprising amount of lycopene, the same red pigment found in raw tomatoes, plus beta-carotene, which your body converts to vitamin A.

The lycopene concentration in watermelon actually rivals or exceeds that of raw tomatoes, a comparison that surprises most people. Beta-carotene shows up in amounts that contribute a small but useful share of vitamin A needs, especially in yellow-fleshed varieties where beta-carotene dominates over lycopene and the flesh takes on a paler hue.

Nutrients in a 286-gram wedge

Those numbers come from standard reference data, but ripeness and variety cause real variation. A fully ripe, high-Brix melon runs slightly higher in sugar and calories, while a just-ripe one sits on the lower end of the range and tastes a little less sweet on the tongue.

How Watermelon Compares to Other Common Fruits

Placing watermelon next to other common fruits on a calorie chart shows just how light it is by comparison. A medium apple at 182 grams runs about 95 calories, slightly above a 286-gram watermelon wedge and delivering far less volume per calorie. Strawberries at one cup hover near 49 calories, almost identical to diced watermelon, though they offer less hydration per gram.

Bananas are far denser, with a medium fruit carrying roughly 105 calories in a much smaller package. Grapes and cherries also sit higher per cup, which makes watermelon one of the leanest fruit choices you can reach for when you want something sweet without a big calorie commitment. The volume advantage matters too, because a cup of watermelon fills more space on the plate than a cup of strawberries at the same weight, and that visual fullness changes how satisfying the portion feels.

Calorie comparison per typical serving

The visual difference on the plate matters as much as the calorie number. A cup of watermelon weighs about the same as a cup of strawberries, but the watermelon physically fills more space because of its higher water content. That generous appearance, not just the calorie count, is what makes a portion feel like enough.

Fitting Watermelon Into a Weight-Loss or Low-Calorie Diet

The combination of high water content, low calorie density, and natural sweetness makes watermelon a natural fit for a calorie-controlled eating plan. A 152-gram cup costs only 46 calories, so you can build a substantial snack around it without touching your calorie budget. The water volume also promotes fullness, a real physiological effect, not just a feeling, that helps bridge the gap between meals.

Eating watermelon between meals is one of the simplest ways to add volume and hydration to your day. It curbs cravings for higher-calorie sweets because the natural sugars satisfy that “something sweet” urge without the concentrated energy of, say, a candy bar. Eating half a melon in one sitting can still exceed 600 calories, so portion awareness matters even with a low-calorie food, and a kitchen scale paired with a known reference (one cup at 152 grams) makes tracking painless.

Practical ways to use watermelon on a diet

• ▸Pre-meal starter: Eat half a cup about 20 minutes before lunch to take the edge off hunger.
• ▸Mid-afternoon snack: Swap a granola bar for a cup of diced watermelon and a tablespoon of pumpkin seeds.
• ▸Post-workout hydration: The water and natural sugars make it a gentle recovery food after light to moderate exercise.
• ▸Yogurt topping: Stir diced melon into plain Greek yogurt for a snack that pairs carbs with protein.

“Watch your portions when the melon tastes extra sweet. A very ripe, high-Brix wedge can carry 10–15% more sugar than a standard one, nudging calories up by a few per slice.

Because the calorie cost stays low even at larger portions, the fruit works as a bridge food on days when you need something sweet between meals. Tracking by the cup rather than the slice also makes logging faster, since the cup reference is what most nutrition apps default to anyway.

Practical Tips for Tracking Watermelon Calories Accurately

The easiest way to log watermelon precisely is to weigh a single slice on a kitchen scale, then enter the gram value into your tracking app. A 286-gram wedge at roughly 0.30 calories per gram gives you a reliable starting point without needing to dig into a database every time, and you can confirm the number against any entry labeled “watermelon, raw.”

If your app defaults to volume units, log the cup measurement, 152 grams at about 46 calories, instead. Most trackers, including MyFitnessPal and Cronometer, pull from the same USDA reference data, so a cup of diced watermelon should show roughly the same number across platforms. For thicker wedges, scale up from the 286-gram reference using the same 0.30 calories-per-gram ratio.

Variables that shift the calorie count

• ▸Variety: Sugar Baby and similar small varieties run slightly sweeter; yellow-fleshed types often carry less sugar.
• ▸Ripeness: A fully ripe melon can carry 10–15% more sugar than one picked a few days earlier.
• ▸Growing conditions: Soil quality, sunlight, and water availability all affect sugar concentration.
• ▸Storage time: A melon stored at room temperature continues to convert starches to sugars after picking.

The rind is essentially zero calories if you eat it (pickled rind is a real thing), but most people discard it. What can quietly add calories is whatever you put on top, a sprinkle of salt, a squeeze of lime, or a dusting of chili powder, none of which carry meaningful energy on their own, but they can become habit-forming toppings worth noting if you’re tracking strictly.

Seedless varieties don’t differ much from seeded ones in calorie content, since the mature seeds you actually swallow are few and small. What changes the number more than anything else is simply how big a slice you cut and how much of it you actually eat, which is why the scale matters more than the variety name on the sticker.

Bottom Line

A standard 286-gram wedge of watermelon costs about 86 calories, and a 152-gram cup of diced fruit runs near 46. The fruit’s 92% water content keeps calorie density around 0.30 calories per gram, low enough that generous portions fit comfortably inside most eating plans. Weigh a slice for precision, log the cup measurement when volume is easier, and treat ripeness and variety as small adjustments rather than dramatic swings.

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