m = ceil((n * log(p)) / log(1.0 / (pow(2.0, log(2.0)))));
        k = round(log(2.0) * m / n);

n

Number of items in the filter

p

Probability of false positives, float between 0 and 1 or a number indicating 1-in-p

m

Number of bits in the filter

k

Number of hash functions

n = 40,000,000, p = 1.0E-6 (1 in 1,000,000) → m = 1,150,207,006 (137.12MB), k = 20