One full head of romaine lettuce contains about 106 calories. That’s for a standard head weighing roughly 626 grams (about 1.4 pounds), which is more lettuce than most people eat in a single sitting. For context, a typical salad uses only a fraction of a head, putting your actual calorie intake from romaine well under 50 calories per serving.
Calories by Serving Size
The calorie math for romaine is straightforward because it’s almost entirely water. At 17 calories per 100 grams, the numbers scale predictably:
- One full head (626 g): 106 calories
- One outer leaf (28 g): 5 calories
- One inner leaf (6 g): 1 calorie
If you’re using romaine hearts, the bagged kind sold in packs of three at most grocery stores, each heart is smaller than a full head. A single romaine heart typically weighs around 175 to 225 grams, putting it in the 30 to 40 calorie range.
Why Romaine Is So Low in Calories
Romaine lettuce is roughly 93% water by weight. A standard 70-gram salad serving contains about 65 grams of pure water, which means you’re eating very little solid material. The small amount of solid content is mostly fiber and a modest amount of carbohydrate, with almost no fat or protein to speak of. This combination of high water content and fiber is what makes romaine one of the lowest-calorie foods you can eat by volume.
Romaine also has a glycemic index of just 1, essentially the lowest possible score. The net carb count is minimal because a significant portion of its carbohydrates come from fiber, which your body doesn’t absorb for energy. A 70-gram serving provides about 2.2 grams of fiber, so a full head delivers roughly 19 to 20 grams, a surprisingly meaningful amount toward the daily recommended intake of 25 to 30 grams.
Nutrients That Make Romaine Worth Eating
The calorie count alone undersells romaine. A full head packs a remarkable amount of certain vitamins relative to its near-zero calorie cost.
Vitamin A is the standout. One head contains over 36,000 IU, which is several times the daily recommended value. This comes primarily in the form of beta-carotene, the pigment that gives romaine its deeper green color compared to iceberg lettuce. Your body converts it into the active form of vitamin A used for vision, immune function, and skin health.
Vitamin K is the other heavy hitter, with a single head providing about 642 micrograms. The daily adequate intake for most adults is 90 to 120 micrograms, so even a few leaves at lunch covers you. Vitamin K plays a central role in blood clotting and bone metabolism.
Folate rounds out the trio. One head contains roughly 851 micrograms, well above the 400-microgram daily recommendation for most adults. Folate is essential for cell division and DNA synthesis, making it particularly important during pregnancy.
Full Head vs. Romaine Hearts
The outer leaves of a full romaine head are darker, tougher, and slightly more nutrient-dense than the pale, crunchy inner leaves that make up a romaine heart. Those darker outer leaves contain more beta-carotene and vitamin K because they’ve had more sun exposure. If you’re buying pre-trimmed romaine hearts for convenience, you’re still getting the same basic nutrition profile, just in a smaller, milder-tasting package with proportionally fewer vitamins per leaf.
For calorie tracking purposes, the difference is negligible. Whether you’re chopping a full head for a family Caesar salad or splitting a romaine heart for a weeknight wrap, you’re working with one of the most calorie-efficient foods available. The real nutritional value of romaine comes not from its energy content but from the vitamins and fiber it delivers for essentially free in your calorie budget.