I have a 4 pound bone-in shoulder roast-- how many people can I feed on it?
you have to account for the weight of the bone and the fat (it also depends on what you're making and how far you're stretching the meat). I would round down and say six or so.
Also depends on what you're doing with it. Something slow-cooked with a rich sauce, like carnitas or pulled pork, will go much farther because you can only eat so much before you're afraid you're gonna throw up. But yeah, figure a minimum of 8 people, more likely 10.
if slow cooked to fall apart tender, bone-in pork shoulder yields around 60% eatable meat. So expect to have 2.5 pounds of finished meat. I try and make sure I have 1/3 a pound per person if it's a main dish. Some eat more, some less. Just adjust depending on how large the appetite of your guests will be and what else you'll be offering for dinner.