I remember it like this:

Finals - 1 match - 2 participants

Semifinals - 2 matches - 4 participants

Quarterfinals - 4 matches - 8 participants

Round of 16 - 8 matches - 16 participants

Round of 32 - 16 matches - 32 participants

In every round, half of the participants are eliminated and the other half moves on. Also the number of matches is reduced by a half every round.