As its name implies, watermelon consist mostly of water (92 percent), and the rest of it is mainly carbs (7 percent).

In an NLEA serving of watermelon (280g), which is approximately one wedge, there are approximately 20g net carbs 1.

Besides water and carbs, watermelon is also a good source of antioxidant vitamins and a modest source of health-promoting proteins. Watermelon also provides minerals in smaller amounts and is a good source of powerful antioxidants.

But does watermelon have a place in a ketogenic diet? Keep reading to find out and also to learn more about watermelon nutrition.

How Many Carbs in Watermelon?

Watermelon is a rich source of carbohydrates considering its serving size. A standard serving of watermelon is one wedge weighing almost 300g (10 oz.) There are around 20g of net carbs* in this serving size. Below are carbs in watermelon in different serving sizes:

  • Watermelon (100g) = 7g net carbs
  • 1 cup diced watermelon (152g) = 11g net carbs
  • 1 whole watermelon (4,500g) = 323g net carbs
  • 10 watermelon balls (122g) = 9g net carbs

As you can probably tell, watermelon is a high-carb fruit, at least from a keto standpoint. Generally speaking, food needs to have 5-10g net carbs per serving to really be keto friendly. A good example is cucumbers that have only 3.1g net carbs per 100g.

Another problem with watermelon is the type of carbs it contains. Like most fruit, the carbs in watermelon are mostly in the form of simple sugars. The most prevailing simple sugar in watermelon is fructose followed by glucose and sucrose. All three sugars raise blood glucose levels to different extents.

Note: Net carbs is a term that refers to total carbs in grams minus fiber. This measurement is used in keto to help determine if a food will affect ketosis.

How many calories in watermelon?

Watermelon is considered a low-calorie food. One wedge provides around 85 calories, which is 4% of the average recommended daily calorie intake. However, from a keto point of view, these calories will are actually too much.

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On a keto diet, only 5-10% of your daily calories should come from carbohydrates. That equals to 100 to 200 calories from carbohydrates or 20-50g per day. Getting 85 of your total daily calories from a single serving of watermelon will put you very close to your daily carb limit, and you won’t have much room left for other meals.

That’s why it’s not recommended to eat watermelon and many other fruits on a keto diet. These foods provide the majority of their calories in the form of carbohydrate. On keto, you should eat either low-carb fruit and vegetables or high-fat food.

Nutritional value of watermelon

Watermelon is considered a somewhat nutrient dense food according to Dr. Fuhrman’s ANDI scores 2. Watermelon provides over 30% of the DV for vitamins C and A. Vitamin C is an important antioxidant vitamin, while some forms of vitamin A in watermelon also function as antioxidants. Antioxidant vitamins are proven to protect against oxidative stress 3.

Other than vitamin C and A, watermelon doesn’t really provide much of other nutrients. A serving of watermelon provides less than 10% DV of B vitamins, vitamin E, and the minerals calcium, iron, magnesium, potassium, and copper. Watermelon is also not a very good source of fiber, providing only 4% of its DV per standard serving.

Watermelon also provides 3% of the DV for protein. And while watermelon is not a source of complete protein, it does contain some non-essential but health-promoting proteins like L-citrulline. Research shows that L-citrulline from watermelon boosts nitric oxide production 4. Nitric oxide is a gas that promotes the relaxation of blood vessels and, in this way, increasing blood flow and improving cardiovascular health.


Nutrition Info: Watermelon NLEA Serving (280g):
Calories 84
Total Carbohydrates 21.1g
Fiber 1.1g
Protein 1.7g
Total Fat 0.4g
Vitamin C 22.7mg
Vitamin A 1593 IU
Potasium 314mg
Magnesium 28mg
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Can You Eat Watermelon on the Keto Diet?

You shouldn’t eat watermelon on a keto diet because it’s relatively high in carbs. However, many keto dieters will still eat watermelon in small amounts. If you can stick to a cup of watermelon a day, you just may be able to stick to your daily 20-50g a day carb limit.

Still, we recommend sticking to low-carb keto fruit, low-carb vegetables, nuts, seeds, and other foods recommended on the keto diet. This will help you stay within the recommended keto macros while also ensuring you’re getting the nutrition you need to stay healthy.

Health Benefits of Watermelon

If you still plan to eat watermelon on a keto diet, you’re probably curious to learn if this fruit provides any health benefits. Below are just a few of science-backed health benefits of watermelon.

1. Antioxidant protection

Studies show eating watermelon increases lycopene concentrations in humans 5. Lycopene is a powerful antioxidant also found in tomatoes. Its antioxidant action can help protect cardiovascular health and prevent certain types of cancer.

2. Improved kidney health

Animal studies found that watermelon can help prevent kidney stones 6. This effect was attributed to steroids and alkanes in watermelon. Besides preventing kidney stones, watermelon also has a mild diuretic effect, meaning it makes you pee more. This can be good for bladder health and can even reduce edema.

3. Improved heart health

Regular watermelon consumption can help reduce high blood pressure. This is due to the amino acid L-citrulline found in watermelon and that converts to L-arginine in the body, a precursor to nitric oxide production.

How to Eat Watermelon on Keto?

While you’d be best off avoiding watermelon on a low-carb and ketogenic diet, there are a few ways to include it and stay in ketosis:

1. Stick to smaller portions

Don’t eat more than 1 cup of watermelon a day and you should be able to stay within your macros. Also, keep in mind that the exact number of carbs in a cup of watermelon can vary based on how much water it contains.

2. Add it to your salads

Some salad recipes call for watermelon as a refreshing ingredient. Take for example this low-carb watermelon salad with feta cheese. It has only 5g net carbs per serving and plenty of fat and protein.

3. Mix it with low-carb fruit

If you like a bowl of refreshing watermelon cubes in the summer, then try mixing it with berries, starfruit, and other low-carb fruits. Make sure to calculate the exact macros for your fruit bowl with watermelon to stay within the recommended carb limits.


  • Watermelon is mainly water, but almost all of its dry weight is composed of carbs.
  • There are 20g net carbs in a standard serving of watermelon or 7g in a 100g serving.
  • All of the carbs in watermelon consist of simple sugars, which are know to raise blood glucose quickly.
  • Because of its high carb content, watermelon is not recommended on a keto diet.
  • Still, you can enjoy watermelon occasionally on keto if you stick to smaller portions.


  1. United States Department of Agriculture. Watermelon, raw. 2018 April -

  2. Comprehensive Aggregate Nutrient Density Index (ANDI) Scores (PDF) -

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