How many episodes does Fullmetal Alchemist: Brotherhood have?

How to get close to this number

Five cours gives sixty-five, and that is essentially the answer. A series planned from the outset to adapt a complete manga will be commissioned for a whole number of quarterly blocks sized to the material, and this one is a little over a year of weekly broadcast. The scheduling grid gets you there without knowing the show.

The history in the explanation is unusual and worth understanding. An earlier adaptation had to invent its own ending because the manga was unfinished; this one was made later specifically to follow the completed source. Two full adaptations of the same manga exist because of a timing problem, which is a rare and very clean illustration of how production constraints shape what gets made.

It also explains the length. A series that knows its ending can plan its pacing across a fixed number of episodes, which is why this one avoids both the filler of an ongoing adaptation and the rushed compression of a series cancelled early. Episode counts are downstream of whether the story was finished before the cameras started.