Here's a handy chart to help determine the right portion sizes for meat joints based on appetite size:

Notes:

• Boneless Meat: Includes lean cuts like beef topside, pork loin, or chicken breast.
• Bone-in Meat: Includes cuts like leg of lamb, rib roast, or chicken thighs.

These portions are for the main course. If the meat is part of a larger meal with substantial sides, you could reduce the quantities slightly. For feasts or special occasions where people may indulge, consider the higher end of the range.