My husband does the same like freelancemomma and I think it clocks in somewhere about 200 calories depending what toppings he adds. He's totally satisfied with it as being pizza for dinner and it satisfies the craving compared to our local takeout with 350 (or more!) calories a slice. And who only eats one slice?
I also make zucchini appetizers by baking the zucchini rounds a little, then adding a dab of sauce, about half a slice of pepperoni and a sprinkle of cheese and basil or italian seasoning. Amazing!
In the worst case scenario at home, you can buy the 100 calorie English muffins and make them that way. You would get 4 halves with toppings for less than 400 calories if you plan the toppings right.
So many ways for pizza to be lower calorie!