How many pizzas do you order from dominoes for 20 ppl?

For a group of 20 people, it's generally recommended to order about 1 to 1.5 pizzas per 3 people, depending on the appetite of the group and whether other food will be served. This would translate to approximately 7 to 10 pizzas. If you expect hearty eaters or if Pizza is the main dish, leaning towards the higher end of that range is advisable.