The UFC played a big role in making rules for MMA that are used all around the world. By 2009, organizations in the United States and many other places agreed on rules called the Unified Rules of Mixed Martial Arts. These rules say that fighters can compete in a ring or a fenced area. They wear gloves with no fingers, but they don't wear shoes or headgear.
They can hit, throw, kick, or wrestle with their opponent, either standing up or on the ground. But there are things they can't do, like head-butting, poking someone's eye, biting, pulling hair, or hitting the groin.
They also can't hit certain parts of the head or back, or use certain moves when the opponent is on the ground. If a fighter breaks a rule, the referee can warn them, take away points, or even disqualify them, especially if it's a serious foul.
According to the Unified Rules, regular MMA fights last for three rounds of five minutes each, with a one-minute rest between rounds. But championship fights have five rounds.
A fighter can win by knocking out the other or by making them give up, either by tapping with their hand or saying they've had enough
If the fight goes on until the end without a knockout or submission, judges decide the winner. They use a system similar to boxing where the winner of each round gets 10 points and the loser gets fewer.
In the United States, referees and judges for MMA are chosen by state athletic commissions. These commissions also do medical checks and test for drugs on fighters.
Different MMA organizations have different weight classes. In the UFC, there are nine weight classes for men. They have limits on how heavy a fighter can be: strawweight is up to 115 pounds (52 kg), flyweight is up to 125 pounds (57 kg), bantamweight is up to 135 pounds (61 kg), featherweight is up to 145 pounds (66 kg),
lightweight is up to 155 pounds (70 kg), welterweight is up to 170 pounds (77 kg), middleweight is up to 185 pounds (84 kg), light heavyweight is up to 205 pounds (93 kg), and heavyweight is up to 265 pounds (120 kg). Although the UFC doesn't officially have a super heavyweight division for fighters heavier than 265 pounds, some other MMA organizations do.
For women in the UFC, there are only two weight classes: strawweight for fighters up to 115 pounds (52 kg) and bantamweight for fighters up to 135 pounds (61 kg). But other MMA organizations have women's fights in more weight classes, like featherweight for up to 145 pounds (66 kg) and atomweight for up to 105 pounds (48 kg).