Watermelon: Calories, Nutrition and Health Benefits

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One cup of diced watermelon (152 g) has about 46 calories, 11.5 g of carbs, 0.9 g of protein and 0.2 g of fat. It is roughly 91% water. A 286 g wedge (1/16 of a medium melon) is about 86 calories, and a whole 4.5 kg melon is about 1,350 calories.

Quick Nutrition Facts

Per 1 cup diced

Nutrient	Amount
Calories	46 kcal
Protein	0.9g
Carbohydrates	11.5g
Fiber	0.6g
Sugars	9.4g
Fat	0.2g
Sodium	2 mg

Macronutrient Breakdown

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NUTRITIONIST'S INSIGHT

Watermelon is mostly water, so a big bowl costs few calories: a 2-cup serving is about 92 kcal. Its glycemic index is high (about 76 in the 2008 international tables) but a 120 g serving carries only about 8 g of available carbs, so the glycemic load is low and a normal portion moves blood sugar modestly. Portion size is what matters: half a melon at one sitting delivers over 650 kcal and 140 g of sugar. The lycopene that gives the flesh its red colour and the amino acid citrulline are the two compounds researchers study most. Human trials link watermelon and citrulline supplements to lower blood pressure, but the doses used in trials (6 g of citrulline a day) are well above what a cup of fruit gives, so treat it as a hydrating, low-calorie fruit rather than a treatment.

Myth Busters

MYTH #1: Watermelon is just sugar water with no nutrition.

TRUTH: A cup gives about 46 kcal along with vitamin C, vitamin A precursors, potassium and lycopene. It is low in calories because it is about 91% water, not because it is empty. It is also low in protein and fibre, so it works as a hydrating snack rather than a meal. Watermelon, raw (FDC ID 167765), USDA FoodData Central; Watermelon and its phytochemicals: lycopene, citrulline and health (PMC7698065)

MYTH #2: People with diabetes must avoid watermelon because of its high glycemic index.

TRUTH: The glycemic index is high (about 76), but a 120 g serving has only about 8 g of available carbs, giving a glycemic load near 6. A cup eaten with protein or nuts is manageable for most people, and the carbs still count toward the daily budget. International tables of glycemic index and glycemic load values: 2008, Diabetes Care (PMC2584181); Watermelon, raw (FDC ID 167765), USDA FoodData Central

MYTH #3: Watermelon is lower in lycopene than tomatoes.

TRUTH: Per gram, fresh red watermelon often contains as much or more lycopene than raw tomato, and it is the main reason the flesh is red. Yellow and orange varieties contain far less. Watermelon and its phytochemicals: lycopene, citrulline and health (PMC7698065); Lycopene and human health review (PMC4464475)

MYTH #4: Eating watermelon at night causes weight gain.

TRUTH: Weight change comes from total daily calories, not from when you eat a fruit. At 46 kcal a cup, watermelon is a low-energy-density choice, and the water content adds volume that helps people feel full. Watermelon, raw (FDC ID 167765), USDA FoodData Central; Watermelon and its phytochemicals: lycopene, citrulline and health (PMC7698065)

MYTH #5: Watermelon seeds are harmful to swallow.

TRUTH: Swallowed seeds pass through the gut without harm. Seeds are edible, and sprouted or roasted seeds add protein, fat and magnesium. Watermelon and its phytochemicals: lycopene, citrulline and health (PMC7698065)

NutriScore by Health Goals

Health Goal	NutriScore	Why This Score?
Weight Loss		46 kcal per cup and about 91% water make it one of the lowest-energy-density fruits, so a large portion fits a calorie deficit. Watermelon, raw (FDC ID 167765), USDA FoodData Central; Watermelon and its phytochemicals: lycopene, citrulline and health (PMC7698065)
Muscle Gain		Under 1 g of protein per cup. The fast carbs and fluid suit post-workout refuelling, but it needs a protein source alongside. Watermelon, raw (FDC ID 167765), USDA FoodData Central
Diabetes		High glycemic index (about 76) with a low glycemic load at 120 g. Keep to one cup, count the carbs and pair it with protein or fat. International tables of glycemic index and glycemic load values: 2008, Diabetes Care (PMC2584181); Watermelon, raw (FDC ID 167765), USDA FoodData Central
PCOS		High glycemic index, but the load per normal serving is low. Smaller portions paired with protein or nuts keep the insulin response gentler. International tables of glycemic index and glycemic load values: 2008, Diabetes Care (PMC2584181)
Pregnancy		Hydrating, has vitamin C and potassium, and is easy to tolerate when nauseous. Wash the rind and eat freshly cut fruit, since pre-cut melon left at room temperature is a food-safety risk. Watermelon, raw (FDC ID 167765), USDA FoodData Central; Watermelon and its phytochemicals: lycopene, citrulline and health (PMC7698065)
Heart Health		Almost no sodium or fat, plus potassium. Reviews report lower blood pressure with watermelon and citrulline in short human trials, though dosing in studies exceeds a cup of fruit. Watermelon's health potential confirmed by review of scientific literature (Fresh Fruit Portal, 2022); Watermelon and its phytochemicals: lycopene, citrulline and health (PMC7698065)

PERSONALIZED NUTRITION

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Blood Sugar Response to Watermelon

Watermelon has a high glycemic index but few carbs per serving, so one cup typically produces a short, modest rise that peaks around 45 minutes and is back near baseline by 2 hours. A whole wedge or half a melon raises the peak. Values are an illustrative curve for a healthy adult, not a measurement. International tables of glycemic index and glycemic load values: 2008, Diabetes Care (PMC2584181); Watermelon, raw (FDC ID 167765), USDA FoodData Central

Typical Glucose Response Curve

Not medical advice

How to flatten the spike

Stick to about 1 to 2 cups instead of eating from a whole melon.
Pair it with protein or fat, such as Greek yogurt, cottage cheese, feta or a handful of nuts, to slow the rise.
Eat it after a meal rather than alone on an empty stomach, and skip juice, which removes the fibre and is easier to overdrink.

Cultural Significance

Watermelon is a summer staple across the US, Europe, the Middle East, India and East Asia, cooled in water or ice and eaten at picnics and street stalls. Cultivation traces back to north-east Africa, and the fruit appears in ancient Egyptian tombs. In Japan, square and premium melons sell as gifts, and in many countries a cut melon is the default way to share fruit with a group.

Compare & Substitute

Watermelon vs Similar Foods

Nutrient	Cantaloupe, diced	Strawberries, halved	Honeydew, diced
Calories	51 kcal	49 kcal	55 kcal
Protein	1.2g	1g	0.8g
Carbohydrates	12.2g	11.7g	13.9g
Fat	0.3g	0.5g	0.2g

Frequently Asked Questions

How many calories are in a cup of watermelon?

One cup of diced watermelon (152 g) has about 46 calories, 11.5 g of carbs, 0.9 g of protein and 0.2 g of fat. USDA lists 30 kcal per 100 g.

How many calories are in a slice or wedge of watermelon?

A 286 g wedge, one sixteenth of a medium melon, is about 86 calories and 21.6 g of carbs. Weigh your slice for a closer number, since wedge sizes vary a lot.

How many calories are in a whole watermelon?

A whole melon of about 4.5 kg of edible flesh is roughly 1,350 calories and 340 g of carbs. A smaller 2 kg personal melon is about 600 calories.

Is watermelon good for weight loss?

Yes, as a swap for higher-calorie snacks. It is about 91% water at 30 kcal per 100 g, so a large bowl is filling for few calories. Watch portions of juice and pre-cut melon sold in sweetened containers.

Is watermelon safe for people with diabetes?

Usually yes in a measured portion. The glycemic index is about 76, but a 120 g serving has a glycemic load near 6. Count the carbs and pair it with protein or nuts; adjust to your own glucose readings.

Does watermelon contain lycopene?

Red watermelon is a rich source of lycopene, the pigment that colours it red, along with the amino acid citrulline. Reviews link both compounds to heart and blood-pressure benefits, with more research needed.