Spinach, mature has 22 kcal per 100 g, with 2.9 g of protein, 2.6 g of carbs, and 0.6 g of fat.
kcal per 100 g22
Values are from USDA FoodData Central, Foundation Foods, FDC ID 1999633 (opens usda.gov in a new tab). A food you buy can differ: check its label.