Dinner plates are most commonly 10 inches in diameter. This size is ideal since dinners usually have more than one aspect to them. A 10-inch dinner plate can hold a protein, a grain, and a vegetable without feeling too overwhelming. If you choose to use smaller plates, say 7 inches or 8 inches, as a dinner plate, your plate will be overflowing with food, or you may even need more than one plate to feed yourself adequately. A larger plate, like 12 inches or even 13 inches, can lead to two things: larger portions than necessary or a plate that feels empty. When buying dinner plates, your best bet is to go for a 10-inch plate, as it is perfect for portion control and is large enough to fit all components of a traditional dinner.