That's probably because it's a tiny filter. In reality you'd calculate the size more appropriately: http://hur.st/bloomfilter?n=4&p=1.0E-20 http://hur.st/bloom

That's probably because it's a tiny filter. In reality you'd calculate the size more appropriately: http://hur.st/bloomfilter?n=4&p=1.0E-20 http://hur.st/bloomfilter?n=4&p=1.0E-20 Here you can give it a false positive rate you're happy with and a number of elements. It'll give you the optimal size and number of hashes to use. Your suggestion would use far too much space.