The number of calories in a panini sandwich can depend on what is in it. A panini that contains steak and white cheddar has approximately 1,050 calories, notes the Panera Bread website. A smoked turkey panini, which includes smoked turkey breast, smoked cheddar, mustard and sun-dried tomatoes, contains 720 calories.
The particular ingredients and added condiments used by different restaurants in making these grilled-sandwiches will affect the number of calories found in one serving size. For example, a turkey pesto panini available at Starbucks contains 480 calories, and 190 of those calories come from fats. This panini also has 32 grams of protein and 42 grams of carbohydrates, notes Starbucks. However, a Lean Cuisine chicken club panini contains 350 calories and 9 grams of fat.