Newark, New Jersey to Beijing, China (Layover) to Seoul, South Korea?

Generally, the size of carry on luggage should not be over 8x16x22 and the weight limitation is 7kg. There is no size limitation of the check in luggage. Did you buy the economy class ticket? If so, you can take at most 20kg check in luggage for free. You need to pay for the extra kilo. You'd better contact your airline for a specific information.