A "utilitarian calculus" is the idea that the ideal possible world could be calculated in a systematic way by adding up units of "utility" (which is usually some kind of pleasurable state, or ability to satisfy desires). Consequentialist utilitarians believe that morality entirely consists of satisfying, or moving towards this ideal world. In theory, a computer that was sophisticated enough could determine exactly what we should or should not do in any given circumstance.

Peter Singer is a utilitarian, who believes that some kind of calculation is possible of the best possible state of affairs, by adding up brain states or something similar to see what produces the most pleasure. He believes that the only moral good is moving towards a world that experiences more "positive" mental states, like pleasure, and less "negative" ones, like suffering and unhappiness (note that he hasn't always been a hedonist utilitarian, but was earlier in his career more of a "preference utilitarian", meaning that people should have their preferences maximized).

David Benatar shares all the basic premises that Peter Singer does - that maximizing pleasure and minimizing suffer is all that we should be doing. However, he is sort of like the super-villain version of Peter Singer. Instead of saying we shouldn't kill animals and we should give our money to charity, he says that we should end the human species. He believes that the calculation does not come up in our favor. Not only do humans generally suffer more than they are happy, so should therefore not exist at all, but we all cause immense suffering in other animals (by destroying the enviroment, and you...killing and eating them). Simply put, it would be better if we never existed, so we should stop having children and end humanity forever.