how many ribs in a lb.?
Assuming a standard trim, meaning that the rack has a longer end and a shorter end that tapers off on one side, and has not been trimmed Memphis-style, ten cooked spare ribs usually make a one pound order at a barbecue joint. I have no idea what the uncooked weight might be. A rack usually has thirteen ribs.
Yes, the other rib types are different. I'm talking standard barbecue spare ribs here.
That will vary according to the type of rib, spare, back, or country style.
This link gives some info on servings per pound by type.
This pic is probably close to 4, 4 1/2 pounds spare ribs.
"is it always 12?"
ime there are no pigs with merely 12 ribs, it's not the way they are born, you see. pigs have 14 on the port side, 14 on the starboard. if someone is selling you 12 bones and tells you that's all the pig had, it's because he ate 2 bones and didn't tell you.
ribs from a 600 lb pig will also weigh more than ribs from a 250 lb pig. pigs can vary enormously in size.
CS ribs are actually made by splitting the blade end of the loin into halves and contain part of the loin eye muscle and either rib or back bones (depending on the half). You don't typically get a rack of these as they are cut into slices by the butcher on a saw (to get even slices), so they're not following the bones. It usually involves about 5 bones worth of the loin, so the section is not as long as either back or spare (side) ribs.
The National Pork Board guide says:
Back ribs..........1.5 servings per pound
Spare ribs.........1.25 servings per pound
Country-Style Loin Ribs.....2 servings per pound