How Many Calories in a Cucumber? The 96 Percent Water Vegetable

Watch someone build a salad and you can almost see the mental math happening over the croutons, the cheese, the dressing. Then the cucumber goes in without a second thought. Nobody counts cucumber. And as it turns out, the instinct is largely correct, though the real numbers are more interesting than the vague idea that it’s “basically water.”

Basically water is accurate, by the way. Slice one open and you’re looking at a vegetable that is roughly 96 percent water by weight, with the remaining sliver split among a little carbohydrate, a trace of protein, and almost no fat. That structure explains nearly everything about cucumber nutrition, from why the calorie count barely registers to why it can’t live up to some of the detox folklore that follows it around.

So let’s put actual numbers on the crunch: what a whole cucumber costs you calorically, what you get in return, and where the honest limits of this vegetable lie.

How many calories are in an entire cucumber?

Start with the number most people actually want: a whole large garden cucumber with the peel on, the standard eight-inch grocery store kind weighing around 300 grams, contains about 45 calories. A smaller medium cucumber closer to 200 grams comes in around 30. For scale, that means an entire large cucumber has fewer calories than half a slice of sandwich bread.

The math is simple because U.S. Department of Agriculture data pegs raw cucumber with peel at about 15 calories per 100 grams. Multiply by weight and you’re done. That per-gram figure also settles a claim you may see floating around online, that cucumber has “4 calories per 100 grams.” It doesn’t. Four calories is closer to what you get from a few thin slices; per 100 grams, the real number is about 15 with the peel and about 12 without it. Still remarkably low, just not magically low.

Variety changes the total mostly by changing the size:

• A long English (hothouse) cucumber, often 300 to 400 grams, runs about 45 to 60 calories.
• A Persian mini cucumber, around 100 grams, has roughly 15 calories.
• A single thin slice weighs about 7 grams and contributes about 1 calorie.

Whichever type is in your crisper drawer, the practical takeaway holds: you could eat an entire cucumber as a snack and barely dent the calorie budget of an average day, which for many adults sits around 2,000 calories.

Why is cucumber so low in calories? The 96 percent answer

Every food’s calorie count is a function of what it’s built from, and cucumber is built almost entirely from water. Depending on the sample, water makes up roughly 95 to 96 percent of its weight. Water has zero calories, so the only energy in a cucumber comes from the thin remainder: about 3.6 grams of carbohydrate, 0.65 grams of protein, and 0.1 grams of fat per 100 grams.

Nutrition researchers describe this with a useful concept called energy density, the calories packed into each gram of food. Cucumber sits near the bottom of the entire food supply at about 0.15 calories per gram. Compare that with potato chips or milk chocolate, both around 5.3 to 5.5 calories per gram. Gram for gram, chips carry roughly 35 times more energy than cucumber. To eat the calories in a single one-ounce bag of chips, you would need to crunch through more than two pounds of cucumber.

This is why low-energy-dense foods matter in real life. Your stomach responds partly to the sheer weight and volume of what you eat, not just its calorie total. Foods that deliver bulk with few calories, mostly water- and fiber-rich vegetables and fruits, let you eat a satisfying portion without a big energy cost. Mayo Clinic frames its “feel full on fewer calories” guidance around exactly this principle, and cucumber is close to the purest example of it you’ll find in a produce aisle.

Cucumber calories by serving size, from one slice to a whole English cucumber

Because cucumber servings vary so wildly, a slice on a sandwich here, half a cucumber with hummus there, it helps to see the numbers laid out by portion. These figures use USDA averages for raw cucumber with peel, at about 15 calories and 95 grams of water per 100 grams.

Serving	Approximate weight	Calories	Water
1 thin slice	7 g	about 1	about 7 g
Half cup, sliced	52 g	about 8	about 49 g
1 cup, sliced	104 g	about 16	about 99 g
Persian mini cucumber	100 g	about 15	about 95 g
Medium cucumber	200 g	about 30	about 190 g
Large garden cucumber (8 in.)	300 g	about 45	about 285 g
English cucumber	350 g	about 50	about 333 g

Two details worth flagging. First, peeling drops the count slightly, to roughly 12 calories per 100 grams, because the skin holds a bit of the fiber and other solids. Second, notice the water column: a single large cucumber delivers more water than a standard eight-ounce glass. That last point matters more than most people realize, and we’ll come back to it when we talk about hydration.

Is cucumber high in sugar?

No, and it’s not close. Raw cucumber contains about 1.7 grams of naturally occurring sugar per 100 grams, which works out to roughly 5 grams in an entire large cucumber. A medium apple, by comparison, carries around 19 grams of sugar; a medium banana, about 14. Even the total carbohydrate load in cucumber is modest: about 3.6 grams per 100 grams, a portion of which is fiber that your body doesn’t absorb as sugar at all.

Botanically, cucumber is a fruit, it grows from a flower and contains seeds, but nutritionally it behaves like the mildest of vegetables. It has essentially no impact worth worrying about on blood sugar in typical portions, which is why non-starchy vegetables like cucumber are generally treated as “eat freely” foods in most mainstream eating patterns, including those designed for people managing blood sugar. Anyone with diabetes should still follow the individualized plan set with their care team, but cucumber is rarely the food that plan needs to restrict.

One caveat belongs here, and it’s about what happens to cucumbers after harvest rather than before. Bread-and-butter pickles and other sweet pickle styles are brined with added sugar, sometimes 7 grams or more per ounce, which can turn a nearly sugar-free vegetable into a modest dessert. The cucumber itself stays innocent; check the label on the jar.

Are cucumbers healthy for losing weight?

They can genuinely help, though not for the reason wellness marketing usually suggests. No food, cucumber included, burns fat or speeds metabolism in any meaningful way. What cucumber does well is arithmetic: it lets you eat more volume for fewer calories, and volume is one of the levers that actually influences how full you feel.

The evidence behind this is the energy-density research mentioned earlier. Studies summarized by Mayo Clinic and others consistently find that people tend to eat a similar weight of food day to day, so shifting that weight toward water-rich, low-calorie foods trims energy intake without demanding heroic willpower. Swap the ounce of chips beside your sandwich for a cup of cucumber slices and you save roughly 135 calories in one small decision. Do something like that daily and the numbers become meaningful over months.

Two honest limits deserve mention. Cucumber alone is not a filling snack for long, because it contains almost no protein or fat, the nutrients that slow digestion and extend satiety. Pairing it with something substantial, hummus, plain yogurt dip, a few nuts, a hard-boiled egg, makes it work far better as an appetite manager. And no single food determines weight outcomes; overall eating pattern, sleep, activity, and genetics all pull weight in that equation. Think of cucumber as an excellent supporting actor in a weight-management plan, not the lead.

Do cucumbers burn more calories than they contain? The negative-calorie myth

You’ve probably heard the claim, usually attached to celery but often extended to cucumber: chewing and digesting it supposedly costs more energy than the food provides, making it a “negative-calorie” food. It’s a tidy idea, and there’s no good evidence it’s true.

Digestion does use energy, a phenomenon nutrition science calls the thermic effect of food. But for a typical mixed diet it consumes only around 10 percent of the calories you take in, and even for fibrous raw vegetables the cost doesn’t come close to flipping the ledger negative. A 45-calorie cucumber might cost your body a few calories to chew, move, and process. You still net the substantial majority of those 45 calories. Researchers who have tested the concept directly, including a small controlled study of celery consumption published in the peer-reviewed literature, found that subjects retained most of the food’s energy, exactly as basic physiology predicts.

Here’s the reframe worth keeping: cucumber doesn’t need the myth. A food that delivers a cup of crunchy volume for 16 calories is already doing something almost nothing else in your kitchen can do. Calling it negative-calorie oversells a vegetable whose real numbers are impressive enough, and myths like this one tend to erode trust in the legitimate case for eating more produce. The legitimate case is strong. Stick with it.

What nutrition do you actually get for those 45 calories?

An honest answer: modest but not trivial. Cucumber is not a nutritional powerhouse in the way spinach or bell peppers are, and pretending otherwise doesn’t serve anyone. Because it’s mostly water, every nutrient arrives in diluted form. Still, eat a whole large cucumber with the peel and here’s the approximate ledger:

• Vitamin K: about 49 micrograms, roughly half the adequate intake for adult women (90 mcg) and about 40 percent for men (120 mcg). This is cucumber’s standout nutrient, and it matters for normal blood clotting and bone health.
• Potassium: about 440 milligrams, a helpful contribution toward the roughly 2,600 to 3,400 milligrams adults are advised to get daily, and relevant to blood pressure regulation.
• Fiber: about 1.5 grams, mostly in and near the skin.
• Vitamin C: about 8 milligrams, close to a tenth of a day’s need.
• Magnesium and small amounts of other minerals: present, though in minor quantities.

Cucumbers also contain plant compounds called cucurbitacins and various flavonoids, which show antioxidant activity in laboratory studies. Be appropriately skeptical of what that means for you: lab-dish findings rarely translate directly into human health outcomes, and there are no rigorous clinical trials showing cucumber compounds prevent or treat disease. The fair summary is that cucumber is a hydrating, very low-calorie vehicle for a respectable dose of vitamin K and some potassium. That’s a real contribution, delivered at almost no caloric cost.

Should you eat the peel? What peeling changes

Keep the peel on if the texture doesn’t bother you. The skin is where cucumber concentrates a disproportionate share of its non-water substance: most of the fiber, a meaningful chunk of the vitamin K, and much of the deep-green pigment that signals the presence of other plant compounds. Peeled cucumber drops to roughly 12 calories per 100 grams from 15, which tells you the peel holds a fifth of the vegetable’s total solids despite being a thin outer layer.

USDA figures make the vitamin K difference concrete: peeled cucumber carries about 7 micrograms per 100 grams versus about 16 with the skin intact. Fiber follows a similar pattern. None of this makes peeled cucumber a poor choice, it’s still a low-calorie, hydrating food, but if you’re eating cucumber partly for what little nutrition it offers, peeling discards a real fraction of it.

A few practical notes. Conventionally grown garden cucumbers are often coated with a thin layer of food-grade wax to preserve moisture; it’s considered safe to eat, but wash the cucumber well under running water and scrub gently before slicing. English cucumbers usually come shrink-wrapped instead of waxed, one reason their thinner skin is pleasant to eat unpeeled. And if a peel tastes bitter, that bitterness comes from cucurbitacins concentrated near the skin and stem end; trimming the ends and peeling that particular cucumber is a matter of taste, not safety, in commercially sold varieties.

Is 2 cucumbers a day too much?

For most healthy adults, no. Two large cucumbers add up to about 60 to 90 calories, around 3 grams of fiber, roughly 100 micrograms of vitamin K, and more than 550 grams of water, the equivalent of two-plus glasses. Nothing in that profile is problematic at daily doses, and eating that much cucumber conveniently covers a good share of the vegetable servings most people fall short on anyway.

Three groups should think a little harder, though. People who take blood-thinning medication are often advised to keep their vitamin K intake consistent rather than low, because sudden swings in vitamin K can affect how the medication works. Two cucumbers daily is a meaningful, steady vitamin K contribution, which is fine, but anyone on this type of medication who plans a big dietary shift should mention it to their care team. Second, some people find that large volumes of raw cucumber cause gas or bloating; cucumbers belong to the same plant family as melons and squash, and their raw bulk plus seeds can be tough on sensitive digestion. Scaling back or peeling and seeding usually solves it. Third, and this is a gentler point: if two cucumbers a day are crowding out other vegetables, variety is losing. Different produce delivers different nutrients, and no single vegetable, however refreshing, covers the spread.

Bottom line: the quantity isn’t the issue. Consistency for those on certain medications, personal digestive tolerance, and dietary variety are the things worth watching.

Does eating cucumber count toward your daily water intake?

Yes, genuinely. The idea that only beverages hydrate you is a persistent misconception. The National Academies’ fluid recommendations, the source of the familiar figures of about 15.5 cups of total daily fluid for men and 11.5 for women, explicitly include water from food, and both Mayo Clinic and Harvard Health note that food typically supplies around 20 percent of a person’s daily fluid intake. Water-rich produce like cucumber, watermelon, lettuce, and celery does most of that work.

Run the cucumber numbers and the contribution is respectable. One large cucumber contains about 285 milliliters of water, more than a standard eight-ounce glass. A cup of slices adds nearly 100 milliliters. On a hot day, a cucumber-heavy salad is quietly doing double duty as both food and fluid.

That said, keep the claim in proportion. Cucumber complements drinking water; it doesn’t replace it, particularly during exercise, illness, or heat, when fluid needs climb and thirst can lag behind actual need. And the popular ritual of cucumber-infused water deserves an honest word: the floating slices contribute flavor and negligible calories, which is lovely, but the hydration comes from the water itself, not from anything the cucumber releases into it. If a few green slices make you drink more water than you otherwise would, that’s a real benefit, achieved through psychology rather than chemistry. Both count.

Do cucumbers detox your body or clear your skin? What the evidence shows

Cucumber has become the unofficial mascot of detox culture, garnishing spa waters and cleanse regimens everywhere. The evidence-based reality is less glamorous and more reassuring: your body already has a detoxification system, your liver and kidneys, and it runs continuously without dietary assistance. No clinical research shows that cucumber, cucumber water, or any cleanse built around them removes toxins, flushes anything, or improves how those organs work. Staying well hydrated does support normal kidney function, and cucumber contributes water, but that’s ordinary physiology, not detoxification.

The skin claims deserve a similarly careful sorting. Adequate hydration supports normal skin function, and severe dehydration visibly affects skin, but drinking extra water or eating extra cucumber beyond your needs has not been shown to clear acne or erase wrinkles. As for the classic image of cucumber slices over the eyes: the effect is real but mundane. A cold, water-heavy slice acts like a small compress, and cool temperatures temporarily constrict blood vessels, which can briefly reduce the look of puffiness. A chilled spoon would do roughly the same job with less ceremony.

Laboratory studies have explored cucumber extracts and compounds like cucurbitacins for antioxidant and anti-inflammatory activity, and the results are scientifically interesting. But findings in cells and animal models are the beginning of evidence, not the conclusion, and human trials are lacking. Eat cucumber because it’s hydrating, nearly calorie-free, and pleasant, all true and sufficient reasons, rather than for promises the research can’t yet back.

Pickles, sushi, and creamy salads: where cucumber calories actually hide

The cucumber itself almost never becomes a calorie problem. What happens to it in the kitchen sometimes does, and the pattern is worth knowing because it repeats across all vegetables.

Take pickles. A dill pickle is still essentially a cucumber, often just 5 to 17 calories depending on size, but the brine loads it with sodium: a single large dill pickle can carry around 1,000 milligrams or more, close to half the 2,300-milligram daily limit that mainstream guidelines recommend staying under. Sweet pickle varieties trade some of that sodium story for added sugar. Neither ruins an otherwise balanced day, but a pickle is no longer nutritionally interchangeable with a fresh cucumber, and people watching blood pressure in particular should treat the jar accordingly.

Prepared dishes tell a similar story through fat rather than salt. A creamy cucumber salad dressed with mayonnaise or sour cream can run 150 to 200 calories per cup, with the cucumber contributing perhaps 15 of them. A cucumber sushi roll typically lands around 130 to 140 calories, almost entirely from the rice. Tzatziki splits the difference: cucumber folded into yogurt with olive oil makes a comparatively reasonable dip, often 30 to 60 calories per quarter cup depending on the recipe.

None of this argues for austerity. Fat helps your body absorb certain nutrients, and a dressing that makes you eat vegetables happily is earning its keep. The point is simpler: when a cucumber dish surprises you calorically, look at what the cucumber is wearing, not the cucumber.

When to talk to a doctor

Cucumber is a low-risk food, but a few situations warrant a professional conversation rather than internet research.

• Itching or tingling in the mouth after eating raw cucumber. This can signal oral allergy syndrome, a cross-reaction seen in some people with ragweed pollen allergy that can involve cucumber, melon, and zucchini. Symptoms are usually mild and confined to the mouth, but an allergist can confirm what’s happening and advise you; interestingly, cooked or pickled cucumber often doesn’t trigger it because heat and processing alter the responsible proteins.
• Hives, facial or throat swelling, vomiting, or any trouble breathing after eating. These suggest a true food allergy and need emergency care immediately, then follow-up with a clinician.
• Persistent bloating, cramping, or changes in digestion that you notice with cucumber or raw vegetables generally. Occasional gas from raw produce is common and benign, but ongoing digestive symptoms deserve evaluation rather than self-diagnosis, since they can reflect anything from a sensitivity to an unrelated condition that happens to flare with high-fiber foods.
• You take blood-thinning medication and plan a major change in vegetable intake. Because vitamin K influences how some of these medications work, consistency matters; your care team can tell you whether your planned change is worth adjusting for.

For everyone else, the guidance is refreshingly simple: wash it, slice it, and enjoy one of the cheapest, lowest-calorie crunches in the produce section.

Frequently asked questions

How many calories are in an entire cucumber?

A whole large garden cucumber, about eight inches and 300 grams with the peel, has roughly 45 calories; a medium one closer to 200 grams has about 30. Long English cucumbers run about 45 to 60 calories, and small Persian cucumbers about 15. The underlying math is USDA data showing about 15 calories per 100 grams of raw cucumber with peel, so the total simply scales with the cucumber’s weight.

Are cucumbers healthy for losing weight?

Yes, as part of an overall eating pattern, because their very low energy density lets you eat filling volume for few calories. Swapping an ounce of chips for a cup of cucumber slices saves roughly 135 calories. Cucumber doesn’t burn fat or boost metabolism, though, and it isn’t filling for long on its own, so pairing it with a protein source like hummus or yogurt dip makes it a far more effective snack.

Is 2 cucumbers a day too much?

For most healthy adults, no; two large cucumbers add only about 60 to 90 calories plus more than two glasses’ worth of water. People taking blood-thinning medication should keep vitamin K intake consistent and mention dietary changes to their care team, since two cucumbers supply around 100 micrograms of vitamin K. Some people also experience gas or bloating from large amounts of raw cucumber, in which case smaller portions or peeling and seeding usually help.

Is cucumber high in sugar?

No. Cucumber contains about 1.7 grams of naturally occurring sugar per 100 grams, so even an entire large cucumber has only about 5 grams, roughly a quarter of the sugar in a medium apple. Total carbohydrate is also low at about 3.6 grams per 100 grams. In typical portions, cucumber has a negligible effect on blood sugar, which is why non-starchy vegetables like it are generally unrestricted in most mainstream eating plans.

Does peeling a cucumber change the calories?

Slightly. Peeled raw cucumber has about 12 calories per 100 grams versus about 15 with the peel on, because the skin holds a share of the vegetable’s fiber and other solids. The bigger difference is nutritional: the peel contains most of the fiber and roughly half of the vitamin K. Washing the cucumber well and eating it unpeeled preserves the most nutrition, but peeled cucumber remains an excellent low-calorie choice.

Is cucumber a carb?

Technically it contains carbohydrate, but very little: about 3.6 grams per 100 grams, some of which is fiber. An entire large cucumber has roughly 11 grams of total carbohydrate, less than a single slice of bread. In practical meal-planning terms, cucumber is classified as a non-starchy vegetable, the category generally treated as minimal-carb and eaten freely in most eating patterns, including carbohydrate-conscious ones.

Can I eat cucumber at night?

Yes. There’s no evidence that eating cucumber, or any low-calorie food, at night causes weight gain or harm; total daily intake matters far more than timing. At about 15 calories per 100 grams, cucumber is one of the lightest possible evening snacks. The only practical caveat is its high water content, which could mean an extra nighttime bathroom trip for people sensitive to fluids close to bedtime.

Do cucumbers have any protein?

Only a trace: about 0.65 grams of protein per 100 grams, which works out to roughly 2 grams in an entire large cucumber. That’s why cucumber alone doesn’t keep hunger away for long, since protein and fat are the nutrients that most extend fullness. Pairing cucumber with a protein-rich partner such as hummus, cottage cheese, plain yogurt dip, or a hard-boiled egg makes it a much more satisfying snack.

Are English and Persian cucumbers nutritionally different from regular ones?

Not meaningfully. All common cucumber varieties are roughly 95 to 96 percent water and deliver about 12 to 15 calories per 100 grams, with similar small amounts of vitamin K, potassium, and fiber. The differences are practical: English cucumbers have thinner skin and fewer developed seeds, Persian minis are smaller and crunchier, and garden cucumbers may be waxed and benefit from a good wash. Calorie totals differ mainly because the cucumbers differ in size.

Does cucumber water have calories, and does it detox your body?

Cucumber-infused water contains negligible calories, typically fewer than 5 per glass, since the slices release flavor rather than substance. It does not detox anything; no clinical evidence supports detox claims for cucumber, and your liver and kidneys already handle that job continuously. What cucumber water genuinely offers is hydration made more appealing, and if it helps you drink more plain water instead of sugary beverages, that’s a real, evidence-aligned benefit.

This article is for general information only and is not a substitute for professional medical advice. Please consult a qualified doctor about your individual situation.