How many sets does a man need to win to take a best-of-five Grand Slam tennis match?

How to get close to this number

Best of five means a majority of five, which is three. Any "best of N" format is won by the first player past half, so the answer is always the next whole number above N over two — and that arithmetic covers every best-of format in every sport.

The asymmetry in the explanation is what makes this worth asking. Men play best of five only at the four Grand Slams; women play best of three everywhere, and men play best of three at every other tour event. So the same sport uses two different match lengths depending on the tournament and the draw.

The consequence is that a men's Grand Slam match is a fundamentally different athletic event from every other professional tennis match — potentially twice as long, with endurance mattering as much as skill. Comparing statistics across formats is comparing two sports, and the longest matches in the sport's history all come from this one format.