Bright red and mouthwateringly juicy, watermelon is a nutrient-dense fruit that makes a refreshing low-calorie snack (1).

When ripe, it provides a great source of natural antioxidants, including lycopene, which is linked to several health benefits, such as protection against heart disease, diabetes, and certain types of cancer (1, 2, 3, 4, 5).

While the best way to know whether a watermelon is ripe is to taste or check its red flesh, this is generally only possible after you buy it.

If you don't want to go for pre-cut products, picking a sweet and juicy watermelon based on its looks can be quite a challenge.

Here are 6 tips to help you take home a delicious watermelon.

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Watermelons come in different sizes and shapes that vary from round to oval to elongated. They can all be a good choice.

Whichever you choose, stick to those with a firm and symmetrical shape, and avoid those with irregular bumps, dents, or cuts.

Irregularities may indicate that the watermelon received inconsistent amounts of water or was not pollinated properly. On the other hand, cuts or dents may point to the presence of insects or fungus (6).

summary

Whether you choose a round, oval, or elongated watermelon, make sure it has a symmetrical and uniform shape without bumps or cuts.

A sweet and ripe watermelon should feel heavy for its size. This usually means that it's full of water and therefore juicier.

In fact, water and fiber content seem to determine a healthy weight in fruits, including watermelon (7).

Watermelons are 91% water — a characteristic that explains its name. Eating water-rich foods like watermelon helps you achieve a greater feeling of fullness per serving while consuming fewer calories (8).

Summary

When choosing a watermelon, go for the one that feels the heaviest for its size.

If you turn a watermelon upside down, you should find a yellow spot, which is also known as the field or ground spot.

This spot shows where the watermelon rested on the ground before being harvested.

A large, yellow spot indicates that it spent more time ripening on the vine and should be sweeter.

On the contrary, a whiter spot suggests that it was picked too soon and didn't reach peak ripeness. Since watermelons don't continue to ripen post-harvest, choosing a watermelon with a whiter spot means you will most likely end up with a plain-flavored one (6).

Summary

Turn around the watermelon and look for a yellow spot, which suggests it reached peak ripeness on the vine. Avoid those with a white spot.

Another way to check the ripeness is by the sound a watermelon makes when you tap or slap it.

Though this method is subjective, it's very popular among watermelon enthusiasts.

In fact, its popularity led researchers to develop a vibration analysis proven to help detect ripeness (9).

A ripe watermelon should have a deep sound when you thump it with your hand or fist, somewhat resembling a tenor. If it has a hollow or flat sound, it's likely overripe (6).

Summary

Try tapping a watermelon with your hand or fist. A ripe one delivers a deep sound, whereas an overripe one sounds hollow or flat.

Checking the firmness of a watermelon refers to the resistance of the rind or skin (6).

A ripe watermelon should have a thick rind that doesn't give easily when pressured. The ones that do are generally overripe.

Also, if you scratch it with your thumbnail, you shouldn't be able to cut through it.

Summary

A ripe watermelon should have a firm rind that doesn't give to pressure and is not easily scratched.

A watermelon's tail refers to the piece of stem that remains attached after the fruit is harvested.

Transporting water and nutrients that allow it to grow, the stem connects the plant's leaves, flowers, and fruit to its roots.

A green stem usually indicates that the watermelon was harvested too early and will not be ripe, as it was still growing. On the contrary, a dried stem points to a ripe watermelon.

Summary

A watermelon's tail is a piece of stem that remains attached after harvesting. A dry stem usually indicates a ripe watermelon.

Damaged or spoiled watermelons may not be safe to eat.

The following signs may help you determine whether a watermelon should be avoided (6, 10):

  • Dark-colored spots. These spots may indicate the presence of fungus or bacteria.
  • Water-soaked flesh. In this case, the flesh of the watermelon begins to disintegrate, sag, and become dark. It could be due to an oversaturation with water or fungal infection.
  • Target cluster. These are target-like configurations believed to be caused by a virus.
  • Rind worm injury. This injury manifests itself as an irregular white to light brown pattern on the rind and may be caused by insect feeding.
  • Internal rind spots. This is a bacterial disease characterized by tan or brown dry tissue on the inner side of the rind.
  • Sour or tangy smell. These are different types of rancid smells that indicate that the flesh has started to ferment.
Summary

Damaged or spoiled watermelons may not be safe to eat. Some signs you should pay attention to include dark spots, rind injuries, and a rancid odor.

Picking a sweet and ripe watermelon can be tricky.

Internal indicators, such as a sweet taste and red flesh, are the only definitive factors when determining the ripeness of a watermelon.

However, some external signs may help differentiate the ripe ones from the immature, overripe, or spoiled ones. These include the melon's weight, sound, and rind appearance.

By following some of the tricks above, you'll be able to pick the perfect watermelon next time you're on the hunt for a refreshing, healthy treat.