A healthy pig can weigh between 2lb - 3/3.5lb - depending on their bone structure & body type - the females will tend to be at the lower end, with the boys getting that bit heftier ! - the main thing to worry about is their weight fluctuation - weigh your piggy regularly, if they lose 2oz then it's wise to take it seriously, carry out some healthchecks so you are armed with useful information to tell your vet - and then contact him without delay. See question below for further weight info.