Never run out (or over-buy) at your cookout.
The standard guideline is ⅓ pound (150g) of cooked meat per adult. Since meat loses 25-40% weight during cooking, buy ½ pound (225g) raw per person for boneless cuts and ¾ pound (340g) for bone-in. Children typically eat half an adult portion. For mixed BBQ, plan 1.5 burgers, 1 hot dog, and 2 chicken pieces per adult as a starting point. Brisket and pulled pork lose ~40% weight; buy 230g raw per person. Ribs: one rack of baby backs serves 2-3 people, spare ribs 3-4. Always buy 10-15% extra — leftovers are better than running out. Consider having a vegetarian option (grilled portobello, corn, veggie burgers) for 10-15% of guests even if not requested.