The calories in vegetable lasagna vary with the ingredients and preparation you use. However, you can use a standard frozen veggie lasagna as the mark against which you compare your favorite recipe to guesstimate how many calories you're about to eat.
The United States Department of Agriculture notes that a typical serving of baked frozen vegetable lasagna is 1 cup. Each serving of veggie lasagna has 314 calories.
Calories from Fat
Every gram of fat has 9 calories. One cup of vegetable lasagna has almost 14 g of fat for almost 123 calories from fat.
Calories from Carbohydrates
According to MedlinePlus, 1 g of carbohydrates has 4 calories. A serving of veggie lasagna has more than 32 g of carbs, giving you more than 128 calories from carbohydrates.
Calories from Protein
A single gram of protein also has 4 calories. Each cup of vegetable lasagna has almost 16 g of protein, accounting for more than 62 calories from protein.