Two brackets
Everyone starts in the winners bracket, which plays out like single elimination. A team that loses there does not go home; it drops into the losers bracket. A loss in the losers bracket ends your tournament.
The grand final reset
The champion of the winners bracket has not lost. The champion of the losers bracket has lost once. If the unbeaten team wins the grand final, it is over. If the losers-bracket team wins, both teams now have one loss, so they play a second game to decide it. That second game is the reset, and it is only played when needed.
How many games
Every team except the champion ends up with two losses, and the champion has none or one. A game makes exactly one loss, so that gives 2n − 2 games for n teams, plus one if the final is replayed. Eight teams: 14 or 15. Sixteen teams: 30 or 31.
The drop order matters
Who drops to which losers-bracket slot decides whether teams meet again too soon. Good brackets send losers in a pattern that keeps teams who just played each other apart until the later rounds. The brackets on this site use a drop order checked by computer for 8 to 64 teams: if the favourites keep winning, nobody replays an opponent before the grand final more than the format forces.
When to choose it
Pick double elimination when every team should play at least two games and the draw matters, as in cornhole, esports and youth baseball tournaments. Pick single elimination when time is short.
Questions
Do byes work the same way?
Yes. Byes go to the top seeds in the winners bracket. A bye does not cost a team a life.
Is the grand final reset fair?
It is the usual rule: the winners-bracket team has to be beaten twice, because it has not lost before. Some events drop the reset to save time; say so before play starts.