The size of a slow or rice cooker depends on how much food you want to cook at once and how many people you want to serve. Generally speaking, a 3-quart slow cooker or a 3-cup rice cooker is suitable for 1 to 2 people; a 6-quart slow cooker or a 6-cup rice cooker is suitable for 4 to 6 people; and an 8-quart slow cooker or a 10-cup rice cooker is suitable for 8 to 10 people. However, these are only rough estimates and may vary depending on the type and amount of food you’re cooking.