The bloomfilter calculator can be used as a standalone tool or in addition to the Bloomfilter Generator. This tool shows the influence of the parameters of a bloomfilter on its false-positive rate.
Therefore you can set the number of bits (m) and the number of hashfunctions (k). With those information the optimal amount of added elements (n) is calculated and also the false positive probability p with this optimal n.
A graph shows the value of p depending on n.