A whole medium cucumber (about 11 ounces or 300 grams) contains roughly 45 calories. A one-cup serving of sliced cucumber has just 16 calories, making it one of the lowest-calorie whole foods you can eat.
Calories by Serving Size
How many calories you get depends on how much cucumber you’re actually eating. Here’s a quick breakdown:
- One cup sliced (104 g): 16 calories
- One-third of a medium cucumber (100 g): about 15 calories
- One whole medium cucumber (300 g): about 45 calories
These numbers apply to standard slicing cucumbers eaten raw with the peel on. English (seedless) cucumbers are slightly longer but have a similar calorie density, so the per-gram count stays about the same.
Why Cucumbers Are So Low in Calories
Cucumbers are 96% water, the highest water content of any food. That leaves very little room for carbohydrates, fat, or protein, which is why the calorie count is almost negligible. A cup of sliced cucumber has an extremely low energy density, meaning you get a lot of volume for very few calories. This matters for weight management: foods with low energy density fill your stomach and can help you feel satisfied while eating less overall.
Vitamins and Minerals
Cucumbers aren’t a nutritional powerhouse, but they do contribute a few useful nutrients. A one-third cucumber serving (about 100 grams) provides:
- Vitamin K: 16.4 micrograms (14% of your daily value)
- Potassium: 147 milligrams (3% daily value)
- Vitamin C: 2.8 milligrams (3% daily value)
Vitamin K is the standout here. It plays a key role in blood clotting and bone health, and eating a whole cucumber gets you to about 40% of your daily need. The potassium and vitamin C contributions are modest per serving but add up if you snack on cucumber regularly.
Blood Sugar Impact
Cucumbers have a glycemic index of about 15 and a glycemic load near 1 for a typical serving. For context, anything under 55 on the glycemic index is considered low, and a glycemic load under 10 is minimal. Cucumbers sit at the very bottom of both scales, so they cause virtually no spike in blood sugar. This makes them a reliable snack for people managing their blood sugar levels.
Cucumbers for Weight Loss
At 16 calories per cup, cucumbers are one of the easiest foods to add volume to a meal without adding meaningful calories. You can eat an entire large cucumber and still take in fewer calories than a single medium apple. That combination of high water content, low energy density, and satisfying crunch is useful if you’re trying to cut calories without feeling like you’re eating less food.
Pairing cucumber slices with a protein source like hummus or cottage cheese makes a more filling snack. The cucumber provides bulk and hydration while the protein keeps hunger at bay longer. Adding cucumbers to salads, wraps, or grain bowls works the same way: more food on your plate, barely any extra calories.