How Many Calories in a Cucumber? 45 for a Whole One, 16 for a Cup
A whole 8¼-inch cucumber with the peel on is 45 kcal, and a cup of slices is about 16. Peeling it takes the per-100-gram figure from 15 kcal down to 10, which is a third of the calories gone with the skin. Those are the two numbers worth knowing; the rest of this page is the portion table and one trap in the USDA data that halves the answer if you miss it.
- Whole, with peel
- 301 g · 45 kcal
- Per 100 g
- 15 with peel · 10 peeled
- Cup of slices
- ~104 g · 16 kcal
- One slice
- 7 g · under 1 kcal
Every USDA portion
| Form | USDA record | Per 100 g | Portion | Weight | Calories |
|---|---|---|---|---|---|
| With peel, raw | FDC 168409 | 15 kcal | cucumber (8¼″) | 301 g | 45 |
| With peel, raw | FDC 168409 | 15 kcal | ½ cup slices | 52 g | 8 |
| With peel, raw | FDC 168409 | 15 kcal | 1 cup slices (derived) | 104 g | 16 |
| Peeled, raw | FDC 169225 | 10 kcal | medium | 201 g | 20 |
| Peeled, raw | FDC 169225 | 10 kcal | large (8¼″) | 280 g | 28 |
| Peeled, raw | FDC 169225 | 10 kcal | small (6⅜″) | 158 g | 16 |
| Peeled, raw | FDC 169225 | 10 kcal | 1 cup, sliced | 119 g | 12 |
| Peeled, raw | FDC 169225 | 10 kcal | 1 slice | 7 g | 0.7 |
| Peeled, raw | FDC 169225 | 10 kcal | 1 stick (4″) | 9 g | 0.9 |
The half-cup trap
The with-peel record has exactly one cup measure and it is stored as half a cup: 52 g. Read it as a full cup and every slice figure you derive comes out at half its real value. A full cup of sliced cucumber with the peel on is 104 g, which is 16 kcal.
There is no “medium cucumber” measure on either with-peel record either. Only the peeled record carries one, at 201 g. A medium cucumber with the skin left on has to be derived, and at 15 kcal per 100 g it lands around 30 kcal.
Two records, one description, different numbers
USDA holds two records both titled Cucumber, with peel, raw, both mapped to the same legacy food code: FDC 168409 and the newer Foundation analysis FDC 2346406. They do not agree. Energy is 15 against 16 kcal, carbohydrate 3.63 g against 2.95 g — a 23% gap — and potassium 147 mg against 170 mg.
There is a second oddity worth knowing if you are chasing fibre: the with-peel record reports 0.5 g per 100 g and the peeled record reports 0.7 g. Peeling a vegetable cannot add fibre. The with-peel figure rests on a single sample, which is the likelier explanation.
At 10 to 16 kcal per 100 g none of this will move your day. It is a clean illustration of why two apps citing “USDA” can still show you different numbers for the same food.
The short version
- Whole cucumber, peel on: 45 kcal at 301 g.
- Cup of slices, peel on: 16 kcal. Peeled: 12 kcal at 119 g.
- Per 100 g: 15 kcal with peel, 10 kcal peeled.
- One slice: under 1 kcal, which is as close to free as food gets.
Logging cucumber slices without the half-cup trap
USDA stores its only with-peel cup measure as half a cup, 52 g, so a full cup of slices is 104 g and 16 kcal, and peeling takes the figure from 15 to 10 kcal per 100 g. The cucumber is the easy case; what sits beside it is the hard one. With PlateLens you photograph the bowl or type or say “a cup of sliced cucumber, peel on, with hummus,” then adjust it in plain words: “it was peeled.” The Dietary Assessment Initiative and the open-source Foodvision Bench have each tested PlateLens: a ±1.1% error in calories on 180 weighed meals in the first study, the same result on 231 other meals in the reproduction.
Frequently Asked Questions
How many calories are in a whole cucumber?
An 8¼-inch cucumber with the peel on is 45 kcal: USDA FDC 168409 gives 15 kcal per 100 g and weighs that cucumber at 301 g. A peeled large cucumber of the same stated length is 28 kcal at 280 g.
How many calories in a cup of cucumber?
About 16 kcal with the peel on and 12 kcal peeled. The with-peel record stores only a half-cup measure of 52 g, so the full cup is derived as 104 g; the peeled record publishes a 119 g cup directly.
Does peeling a cucumber change the calories?
Yes, by about a third per 100 g: 15 kcal with the peel against 10 kcal peeled. The skin carries a meaningful share of the carbohydrate and most of the colour.
How many calories in a slice of cucumber?
USDA weighs one slice at 7 g on the peeled record, which is 0.7 kcal. A 4-inch stick is 9 g, or 0.9 kcal.
Why do two USDA records for cucumber disagree?
USDA holds an older SR Legacy record and a newer Foundation analysis under the identical description. They report 15 against 16 kcal per 100 g and 3.63 g against 2.95 g of carbohydrate. The newer record is the more recent laboratory work; the older one has the portion measures.
How can I keep tabs on a cucumber salad without adding up every ingredient?
PlateLens can log the whole bowl from one photo or a sentence such as “sliced cucumber with a spoon of olive oil,” and takes corrections in plain words. The slices barely register, about 16 kcal for a full cup with the peel, so the real question is everything beside them on the plate. The ±1.1% calorie error that the Dietary Assessment Initiative measured for PlateLens on 180 weighed meals has since been reproduced by the open-source Foodvision Bench on 231 other meals.
Where these numbers come from
- USDA FoodData Central records retrieved on 20 September 2026. All nutrient values are per 100 g; every portion figure multiplies that value by the record’s own gram weight and divides by 100, rounding only at the end. Retrieval confirms the published record, not a new laboratory analysis.
- FDC 168409: Cucumber, with peel, raw (SR Legacy). FDC 2346406: Cucumber, with peel, raw (Foundation). FDC 169225: Cucumber, peeled, raw.
- The one-cup with-peel figure is derived by doubling the record’s own half-cup measure of 52 g, and is marked as derived in the table.