How many rounds are there in the MLB Home Run Derby?

There are 3 rounds.

The first round has 8 players and the top 4 players advance to the second round.

The second round has 4 players and the top 2 players advance. The totals for the first round are counted again in the second round - a good first round can sometimes guarantee entrance to the final round.

The final round is head-to-head.