Bbq for 100

If you want 1 sandwich per person, 1/4lb serving and assume a 60% yield from raw weight then you need 41.67 total raw pounds. How many butts you will need will depends on the size of each butt, roughly 6 7 lb butts.

Now, how much you really need depends on: are they all adults, men, women, children, how many sides will be offered, just one sandwich per person or can they get seconds, are they serving up the sandwiches themselves, etc etc etc.

What Neil says

I always factor in a 1/2# uncooked per person, typically end up with about 20% leftover or so, but it lets you use the bigger seeded bunds instead of those little dinky ones.

I calculate 50% yield, that takes care of big eaters and is easier on my pea brain. I usually have some leftovers that I leave with host and that's a good promo and cheap insurance.