1gr protein = 4 cals
1gr carb = 4 cals
1gr fat = 9 cals

It's pretty easy to see where your calories are coming from if you can remember that. Most protein powders have 20-25gr of protein per scoop...which is around 80-100 calories from protein. It depends on the size of the scoop also...but if yours has 26gr of protein, then you're getting about 104 cals from protein. So the other 150 calories are from fat or carbs. Probably both. Fat slows the digestion of protein, so in my post workout shakes, I use a lower fat milk. Before bed, I mix casein and whole milk.