How Many Calories in a Cucumber

A whole cucumber contains extremely few calories, making it one of the lowest-calorie vegetables available. A standard, unpeeled cucumber weighing around 300 grams contains just about 45 calories in total. Most of its weight comes from water, which makes it filling and hydrating without contributing significant energy to your diet. Whether eaten raw, sliced into salads, or blended into smoothies, cucumbers deliver volume and crunch without loading your calorie count.

Calories by Size and Preparation

A medium-sized cucumber weighs approximately 200 to 250 grams and contains 30 to 35 calories. A large cucumber, closer to 300 grams, reaches around 45 calories. If peeled, the calorie count drops slightly since the skin contributes a small amount of fibre and minimal carbohydrates. A single thick slice of cucumber has just 1 to 2 calories, making it virtually negligible when portioned into a salad or used as a garnish. Even a full cup of sliced cucumber comes in under 20 calories, making it ideal for snacking or meal volume.

Nutritional Breakdown of a Cucumber

Cucumbers are mostly water, over 95 percent and are naturally low in fat, sugar, and carbohydrates. A whole unpeeled cucumber contains around 11 grams of carbohydrates, including 2 grams of fibre and a small amount of natural sugar. It also delivers about 2 grams of protein and virtually no fat. Cucumbers are a source of vitamin K, potassium, magnesium, and small amounts of vitamin C. The skin contains many of these nutrients, so keeping it on boosts the nutritional value.

Health Benefits of Cucumbers

Despite being low in calories, cucumbers offer several health benefits. Their high water content helps maintain hydration and supports healthy digestion. The small dose of fibre they contain promotes bowel regularity, and the antioxidants found in the peel including flavonoids and tannins help reduce inflammation in the body. Because they are so low in energy and high in volume, cucumbers can help fill you up during meals and prevent overeating. They’re especially helpful in calorie-controlled or high-volume eating plans where satiety is a priority.

Downsides of Cucumbers

Cucumbers are generally well tolerated, but they don’t offer much in the way of macronutrients or calories, which means they shouldn't be your main source of energy or nutrients. Some people may also experience mild bloating or gas when eating large quantities of raw cucumbers due to their soluble fibre and water content. Pickled cucumbers, such as gherkins or dill pickles, can also be high in sodium depending on how they're prepared, which may affect water retention or blood pressure in sodium-sensitive individuals.

How Cucumbers Impact Your Diet

Cucumbers are an excellent tool for those trying to lose weight or maintain a calorie deficit. They can bulk up meals, add crunch, and provide visual volume without significantly increasing the calorie load. You can use them as a base for salads, as a low-calorie substitute for crackers or chips when dipping, or as a palate refresher between meals. Their high water content can also help prevent dehydration-driven hunger, which is often mistaken for the need to eat. Because they are low in carbs and calories, cucumbers work well in low-carb, keto, vegan, and intermittent fasting diets.

Glycemic Index of Cucumbers

Cucumbers have a very low glycemic index, typically under 15, and an equally low glycemic load due to their minimal carbohydrate content. This means they have virtually no effect on blood sugar levels, even when eaten in generous amounts. For people with diabetes or those trying to manage insulin levels, cucumbers are one of the safest and most blood sugar–friendly vegetables to include.

How Cucumbers Are Grown and Prepared

Cucumbers are typically grown in warm climates and are harvested before full seed development for a firmer texture. They are often eaten raw but can also be lightly pickled or added to cold soups and smoothies. Peeled cucumbers are milder in flavour, while unpeeled cucumbers provide more texture and nutrition. English or seedless cucumbers, which have thinner skins and fewer seeds, are especially popular for raw use because they require little to no preparation.

What’s in a Cucumber?

A raw cucumber contains only one ingredient, cucumber. There are no added sugars, fats, or preservatives. When eating fresh cucumber, especially from a whole food source, you’re getting pure hydration, fibre, trace minerals, and antioxidants with an incredibly low calorie cost. Processed cucumber products, such as pickles or cucumber juice, may include added salt, vinegar, or sweeteners, so checking the label is important for accurate calorie tracking.

A Healthier Alternative?

There’s little reason to avoid cucumbers but if you're looking for slightly more fibre or nutrients per calorie, vegetables like celery, zucchini, or bell peppers offer similar crunch with added vitamins or variety. However, cucumbers are hard to beat as a hydrating, low-calorie, versatile vegetable that works in nearly any meal plan without taking up much of your calorie budget.

Why Cucumbers Are a Calorie-Tracking Loophole

For people counting calories, cucumbers are often logged as zero-calorie food, especially in meal plans or fasting routines. Technically, cucumbers do have calories about 15 per 100 grams but the number is so low that in most diet apps and trackers, it’s often rounded down to zero or marked as "free." This makes cucumbers especially helpful in volume eating strategies, where you need to satisfy hunger with as few calories as possible. That said, if you're eating large amounts (like cucumber noodles or cucumber-based smoothies), it may be worth tracking them for accuracy.

Cucumber vs Lettuce or Celery: Which is Lower in Calories?

While all three are low-calorie staples, cucumbers sit between celery and lettuce in calorie density. Celery has slightly fewer calories per gram, while lettuce, especially iceberg has a touch more due to its trace carb content. Cucumbers are more hydrating and satisfying to chew, giving them a slight edge in satiety and versatility, especially when used in snacks or meals where texture matters.

Cucumber Skin: Calorie Impact and Nutrition

Keeping the skin on your cucumber doesn't change the calorie count much, maybe one or two calories extra per cucumber but it significantly boosts the fibre and antioxidant content. The skin contains chlorophyll, flavonoids, and silica, which support skin health and digestion. Unless the cucumber is waxed or conventionally farmed (in which case you may want to wash or peel it), leaving the skin on is a smart move for maximum nutrition without any real calorie cost.

Cucumbers and Appetite Psychology

Cucumbers work so well in dieting not just because they're low in calories, but because they play into the psychological experience of eating. They provide crunch, water content, and volume, three things that make your brain feel like you’re consuming more than you are. When eaten before or alongside higher-calorie foods, cucumbers can reduce total intake by increasing physical fullness before energy-dense items hit your plate.

Pickled Cucumbers: Not Always Calorie-Free

Pickles are often assumed to be calorie-free because they’re derived from cucumbers, but that’s not always the case. While dill pickles generally stay under 5 to 10 calories each, sweet pickles or bread-and-butter varieties can contain added sugar, bumping the total to 25–40 calories per spear or slice. If you're using pickles in sandwiches, wraps, or as snacks, check the label as some brands pack in far more sugar than you'd expect from something that looks like a vegetable

Are Cucumbers “Negative Calorie” Foods?

There’s a popular myth that cucumbers and foods like them, take more energy to digest than they provide, making them “negative calorie.” While it’s not literally true, cucumbers come close. The thermic effect of food (TEF) the energy it takes to chew, digest, and metabolise is real, and for something with as few calories as a cucumber, your body may burn a significant percentage of those calories during digestion. It’s not enough to create a net loss, but it helps explain why cucumbers feel so light and diet friendly.

Summary

A whole cucumber contains around 45 calories, with most of its weight coming from water. It's extremely low in fat, carbs, and protein but provides useful fibre, hydration, and trace nutrients. Cucumbers are a smart addition to any diet that prioritizes volume, weight control, or blood sugar stability. Whether eaten raw, sliced, or blended, cucumbers offer a satisfying crunch with almost no calorie cost, making them one of the most efficient and guilt-free foods you can eat.