The Agriculture Department states that a 2-ounce slice of pizza contains 140 calories. However, it's difficult to measure the exact calories per slice because the sizes, ingredients and toppings vary by pizza establishment.
For example, as of 2014, Pizza Hut's 4.4-ounce slice of pizza contains 253 calories, while a 4-ounce slice of Godfather's pizza has 271 calories. Some pizza parlors serve bigger portions of pizza. Ray's of Greenwich Village serves an 8.5-ounce slice of pizza that contains 613 calories, while Two Boots to Go serves 7-ounce slices of pizza that contain 482 calories. Some pizza makers provide nutrition information on the pizzas they serve, and it's advisable for weight watchers to refer to it.