Generally, there are various sizes on the market and there is no exact definition for how large the air fryer is. As far as I am concern, you need to think about how much food you need with it. If you are deeply dependant on an air fryer and you have a big family, I recommend you to choose a air fryer with large capacity over 8 Qt. Beyond that, a large size air fryer can provide enough space for big food like chicken and fish. While if you have one or two people in family, you can get by with a smaller model. However, the extra large air fryer means more space-consuming so take the space into account when you buy it.