i usually sprout just a couple, even just one or two.
no one has ever complained about my seeds NOT germinating
for them. i mean, what are the chances that the one or two i pick out are the only ones for a mile that will sprout? i know not of a rule of thumb. i would worry more about seeds that are less than full, have the blackness on them or whatever else, before thinking that they would not sprout because of no OBVIOUS reason...keep testing them anyway, though, just in case....as we all SHOULD...eric