What is a watermelon made up of?

January 5, 2026 •

3 min read

An impressive 92% of a watermelon is water, making it one of the most hydrating fruits available. But its composition is far more complex than just H2O, offering a host of beneficial nutrients, vitamins, and unique plant compounds. This comprehensive breakdown explores the inner workings of this beloved fruit.

Quick Summary

Watermelon consists primarily of water (92%) and natural sugars, complemented by essential nutrients such as vitamins A and C, minerals, and powerful antioxidants like lycopene and citrulline.

Key Points

High Water Content: Composed of about 92% water, making it exceptionally hydrating.
Rich in Lycopene: A powerful antioxidant responsible for its red color, which may offer health benefits like reduced inflammation and cancer risk.
Source of Citrulline: The rind contains high levels of this amino acid, which can improve blood flow and reduce muscle soreness.
Nutrient Dense: Provides a good source of vitamins A and C, several B vitamins, as well as minerals like potassium and magnesium.
Low Calorie: Offers significant nutrients with a very low-calorie count, making it a satiating and healthy sweet treat.
Whole Fruit Usability: The seeds are rich in minerals and fats, and the rind is high in fiber and citrulline and is edible.
Hydration Benefits: The high water content helps regulate body temperature and aids various bodily functions.

The Core Composition: Water and Carbohydrates

Primarily Water

As its name suggests, the defining characteristic of watermelon is its water content. Comprising roughly 92% of its weight, this high percentage makes it exceptionally effective at quenching thirst and contributing to daily fluid intake. The water is stored within the fruit's numerous cells, giving it its juicy, refreshing texture. The importance of hydration for bodily functions, including nutrient delivery and temperature regulation, cannot be overstated, and watermelon provides a delicious way to achieve this.

Natural Sugars: The Source of Sweetness

The remaining percentage of the watermelon's mass is largely made up of carbohydrates, primarily in the form of natural sugars. For every 100 grams of raw watermelon, approximately 7.6 grams are carbohydrates, with about 6.2 grams being simple sugars like fructose, glucose, and sucrose. This sweet flavor profile makes watermelon a popular low-calorie treat, with about 30 calories per 100 grams.

A Rich Profile of Vitamins and Minerals

Beyond its core structure, watermelon is a surprisingly nutrient-dense fruit. While low in overall calories, it provides a solid dose of essential vitamins and minerals that are vital for human health.

Essential Vitamins

Vitamin C: A powerful antioxidant that is crucial for immune function and skin health, as it helps in the production of collagen. A single serving can provide a significant portion of your daily requirement.
Vitamin A: Watermelon is a good source of beta-carotene, which the body converts into vitamin A. This vitamin is essential for healthy skin, vision, and immune function.
B Vitamins: The fruit contains smaller but valuable amounts of B vitamins, including B6 (pyridoxine) and B1 (thiamine), which support the body's energy production and nerve function.

Key Minerals

Potassium: Important for controlling blood pressure and supporting heart health, potassium is one of the most prominent minerals found in watermelon flesh.
Magnesium: This mineral plays a key role in energy production, nerve function, and blood pressure regulation.
Other Minerals: The rind and seeds also contribute to the mineral profile, containing trace amounts of phosphorus, calcium, iron, and zinc.

Powerful Plant Compounds: The Bioactive Elements

Lycopene: The Red Antioxidant

Watermelon is one of the richest dietary sources of lycopene, a powerful antioxidant and carotenoid responsible for its vibrant red color. In fact, fresh watermelon contains even more lycopene than a tomato. Lycopene has been linked to numerous health benefits, including a reduced risk of certain cancers, protection against oxidative stress, and improved cardiovascular health.

Citrulline: The Hidden Amino Acid

Watermelon, particularly its white rind, is an abundant source of the amino acid citrulline. In the body, citrulline is converted into another amino acid, arginine, which is involved in nitric oxide synthesis. Nitric oxide helps relax and dilate blood vessels, which can lead to lower blood pressure and improved athletic performance by reducing muscle soreness.

More Than Just the Flesh: Exploring the Whole Watermelon

While most people enjoy the juicy red flesh, the entire watermelon is usable and contains valuable nutrients. The rind and seeds possess their own unique nutritional profiles.

Nutrients Found in Different Parts of Watermelon

Watermelon Flesh: The main source of lycopene and contains a balanced mix of sugars, vitamins, and minerals. It's the most hydrating part of the fruit.
Watermelon Rind: Contains higher levels of the amino acid L-citrulline and is lower in sugar than the flesh. It also provides a small amount of fiber. Pickling or cooking the rind are popular methods of consumption.
Watermelon Seeds: Rich in protein, magnesium, and healthy fatty acids. They can be roasted and enjoyed as a crunchy snack.

A Comparative Look at Watermelon Flesh vs. Rind


Component	Watermelon Flesh	Watermelon Rind
Water	Very High (approx. 92%)	High (but less than flesh)
Sugar	High	Low
Fiber	Low (0.4 g per 100g)	High (relative to flesh)
Lycopene	High, especially in red varieties	Very Low (trace amounts)
Citrulline	Moderate	High
Fat	Trace Amounts	Trace Amounts
Use	Eaten fresh, juiced	Pickled, cooked, stir-fried

Conclusion

What is a watermelon made up of is a question with a complex and fascinating answer. It is far more than just water and sugar. The fruit's impressive composition includes a hydrating core, a wealth of essential vitamins and minerals, and potent bioactive compounds like lycopene and citrulline, all of which contribute to its significant health benefits. By understanding its full nutritional profile, from the juicy flesh to the often-overlooked rind and seeds, we can appreciate this summer staple for its comprehensive nourishment, not just its refreshing taste.

Frequently Asked Questions

Botanically, watermelon is a fruit, as it develops from the flower's ovary and contains seeds. However, it is also considered a vegetable because it belongs to the cucurbitaceae family, is grown as a vegetable crop, and is often prepared and consumed like a vegetable.

The vibrant red color of red-fleshed watermelon varieties is caused by the high concentration of the antioxidant lycopene. The level of lycopene can vary significantly among different cultivars.

Compared to many other fruits, watermelon has a relatively low sugar content by weight, mostly comprising fructose, glucose, and sucrose. Its high water content means that a typical serving contains a modest amount of total sugar.

The white rind contains high levels of the amino acid L-citrulline, which supports cardiovascular health by improving blood flow. The rind is also a source of dietary fiber and other valuable nutrients.

Yes, watermelon seeds are edible and nutritious. They are a good source of protein, magnesium, and healthy fats. They can be eaten raw, or roasted and seasoned for a snack.

Absolutely. With a water content of approximately 92%, watermelon is an excellent food for hydration, especially during hot weather or after exercise.

While not a primary source, watermelon does contain a small amount of dietary fiber, especially in the rind. The combination of water and fiber aids in healthy digestion and regular bowel movements.