Here is a very helpful tool for dieters - a online calorie counter database. Here you can look up every type of food and find out their nutritional data. I just looked up plain flour that I use to make my own bread. To make one loaf I use 2 cups of flour and I found out that those 2 cups is 910 calories. The other ingredients (water, salt and yeast) had very small amounts, the yeast 35 calories. So for me to make a 2 pound loaf of bread the calories would be about 950 total. Compare that with the store bought loaf with 150-200 calories a slice and I think that I am doing better by making my own bread.
Here is the link to the calorie counter