A medium lemon contains about 15 to 17 calories, making it one of the lowest-calorie fruits you can eat. Even a large lemon stays well under 25 calories. Most of those calories come from a small amount of natural sugar and carbohydrates, with virtually no fat or protein.
Calories by Lemon Size
The FDA lists a medium lemon (58 grams, roughly 2 inches across) at 15 calories. USDA nutrition data for the same size puts it at 17 calories. The small difference comes down to rounding, but either way you’re looking at a negligible amount of energy. A larger lemon weighing around 84 grams lands closer to 22 calories when you scale up proportionally.
If you’re just squeezing lemon juice into water or over a dish, the calorie count drops even further. The juice from one whole lemon contains roughly 11 calories. A single wedge or a tablespoon of juice adds about 3 to 4 calories.
Lemon Juice vs. Whole Lemon vs. Zest
How you use a lemon changes its nutritional profile slightly. The juice is mostly water and citric acid with a small amount of sugar. A whole lemon eaten with its flesh delivers more fiber and a bit more carbohydrate. Lemon zest, the grated outer peel, contains just 3 calories per tablespoon along with about 0.6 grams of fiber and 1 gram of carbohydrate. Zest is a useful way to add intense lemon flavor to food with almost zero caloric cost.
What Else Is in a Lemon
Beyond calories, lemons are best known for their vitamin C. The juice of one lemon provides about 22 milligrams of vitamin C, which covers roughly a quarter of the daily recommended intake. That makes a single lemon a meaningful source of this nutrient, even if you’re only using the juice.
Lemons are so low in digestible carbohydrate that Diabetes Canada doesn’t even assign them a glycemic index value. They contain fewer than 15 grams of available carbohydrate per serving, which means they have little to no measurable effect on blood sugar. This is one reason lemon juice in water is a popular choice for people watching their glucose levels.
How Lemons Compare to Other Citrus
Lemons are among the least caloric citrus fruits, largely because you consume less of them at a time and they contain less sugar than their sweeter relatives.
- Lemon: 15 calories (1 medium, 58 g)
- Lime: 20 calories (1 medium, 67 g)
- Grapefruit: 60 calories (half a medium, 154 g)
- Orange: 80 calories (1 medium, 154 g)
Oranges and grapefruits are significantly larger and sweeter, which accounts for most of the difference. On a gram-for-gram basis, lemons still come out lower because of their minimal sugar content.
Lemons and Weight Management
Because lemons are so low in calories, they’re often promoted as a weight loss tool. The reality is simpler than most marketing suggests. Adding lemon to water doesn’t burn fat or speed up your metabolism in any meaningful way. A study on a “lemon detox” program did find reductions in body fat and insulin resistance among participants, but those results came from extreme caloric restriction (the participants were essentially fasting), not from any special property of lemon itself.
Where lemons genuinely help is as a flavor substitute. Using lemon juice in place of calorie-dense dressings, sauces, or sugary drinks can reduce your overall intake without sacrificing taste. A squeeze of lemon over grilled fish or salad adds brightness for 3 or 4 calories instead of the 70 to 120 calories in a typical serving of dressing.