Current modern rules per the Association of Boxing Commissions are as follows.
A boxing match consists of a determined number of three-minute rounds, a total of up to 12 rounds (formerly 15). A minute is typically spent between each round with the fighters in their assigned corners receiving advice and attention from their coaches. The fight is controlled by a referee who works in the ring to judge and control the fight, rule on the ability of the fighters to fight safely, count knocked-down fighters, and rule on fouls.
Deciding the winner
There are three judges at ringside to score the fight and assign points to the boxers, based on connecting punches, defense, knockdowns, and other subjective measures—such as who lands the more accurate punches (e.g., a punch that lands squarely on the opponent's chin versus one that lands on the shoulder and then continues through to the head). Because of the open ended nature of judging, there have been many controversial rulings.
If the fight goes to the conclusion of the scheduled number of rounds without a knockout or technical knockout, then the fighter with the higher score at the end of the fight is ruled the winner and the three judges rule it as, a. a unanimous decision b. a split decision or c. a draw.
Win by Knockout (KO)
If a fighter is knocked down during the fight, determined by whether the boxer touches the canvas floor of the ring with any part of their body other than the feet as a result of the opponent’s punch and not slip, as determined by the referee, the referee begins counting until the fighter returns to his or her feet and can continue. Should the referee count to ten, then the knocked-down boxer is ruled “knocked out” (whether unconscious or not) and the other boxer is ruled the winner by knockout (KO).
Win by Technical Knockout (TKO)
A “technical knockout” (TKO) is possible as well, and is ruled by the referee, fight doctor, or a fighter’s corner if a fighter is unable to safely continue to fight, based upon injuries or being judged unable to effectively defend himself. There is also the “three-knockdown rule”, in which three knockdowns in a single round result in a TKO. A TKO is considered a knockout in a fighter’s record.
Standing eight count
A “standing eight” count rule may also be in effect. This gives the referee the right to step in and administer a count of eight to a fighter that he feels may be in danger, even if no knockdown has taken place. After counting the referee will observe the fighter, and decide if he is fit to continue. For scoring purposes, a standing eight count is treated as a knockdown.
Violations of these boxing rules may be ruled a “foul” by the referee, who may issue warnings, deduct points, or disqualify an offending boxer, causing an automatic loss, depending on the seriousness and intentionality of the foul. An intentional foul that causes injury that prevents a fight from continuing usually causes the boxer who committed it to be disqualified. A fighter who suffers an accidental low-blow may be given up to five minutes to recover, after which they may be ruled knocked out if they are unable to continue. Accidental fouls that cause injury ending a bout may lead to a “no contest” result, or else cause the fight to go to a decision if enough rounds (typically four or more, or at least three in a four-round fight) have passed.
Boxers are prohibited from hitting below the belt, holding, tripping, pushing, biting, spitting on or wrestling their opponent. Boxers typically wear shorts or trunks with the waistband raised so the opponent is not allowed to strike the groin area. They also are prohibited from kicking, head-butting, or striking with any part of the arm other than the knuckles of a closed fist. They are prohibited as well from hitting the back, the back of the head/neck (commonly called a “rabbit-punch”), or the kidneys. They are prohibited from holding the ropes for support when punching, holding an opponent while punching, or ducking below the level of the opponent's belt. If a “clinch” – a defensive move in which a fighter wraps his/her arms around those of the opponent and holds on to create a pause – is broken by the referee, each fighter must take a full step back before punching again. Alternatively, the referee may direct the fighters to “punch out” of the clinch. When a boxer is knocked down, the other boxer must immediately cease fighting and move to the furthest neutral corner of the ring until the referee has either ruled a knockout or called for the fight to continue; however, once a fighter is knocked down, the referee must count to eight seconds before the fight can continue.