am pretty new to raising ducks myself (have had them for about 7 or 8 weeks now) and getting geese this fall (two of them), these are our dimensions for our coop and space we give our birds.
the coop is 45 sq ft (maybe 46 or 47 sq ft but for math we just say 45) and its going to be housing 5 birds (3 ducks, two are Swedish and the other is going to be a runner and two geese, one is a Toulouse and the other is an African) meaning we have 9 sq feet a bird. my book recommends 5 for ducks and 10 for geese. so am happy with the space we have for inside,
outside is a bit different, i have talked to the breeder am getting my birds from and have read many books on the subject of waterfowl. the breeder am getting my birds from recommend's 100 sq feet (or 10 by 10) for each goose/duck and told me any less and your not going to have any grass growing. my books tell me 10 sq ft per duck and 20 sq ft per goose out side.
outside for me, am using 28 sq ft per duck/goose its just the number the run made out per bird. all i know is they need a lot of space for geese. to forage there food. (also to note we fenced the roof as well with hardware cloth, hoping for nothing to get in, so many coons we have)
our whole chicken raising experience has always been too many for the space we have (were on 10 acres, but its infested with coons and coyotes so no free ranging for me) so we went for as much space as we could give.