A catch weight is a term used in combat sports such as boxing and mixed martial arts to describe a weight limit for a fight that does not fall in line with the traditional limits for weight classes. In boxing, a catch-weight is negotiated when the weigh-ins are conducted a day before the fight.
Strictly speaking, a catch-weight in boxing is used to describe a weight limit for a fight that does not fall in line with the limits for the expanded weight classes; after the traditional rules of "day of" fight were changed to "day before" fight weigh-ins and after the traditional eight weight divisions were expanded to 17 weight classes.
An agreed weight was used to describe a catch-weight in the traditional way, when only eight (8) division limits existed and all weigh-ins were done "day or hours" before the fight. A historical marker that points to when "day of" fight ended is the advent of television. In boxing and in Muhammad Ali's time, they started televising the weigh-in proceedings to promote fights necessitating a "day before" fight weigh-in.
With modern conditioning and training methods, today's fighters are able to cut weight for a "day before" fight weigh-in and regain the same weight on "day of" the fight.
The purpose of a catch-weight is to compensate for the ability of bigger boxers to cut weight before a "day before" fight weigh-in and re-build to a weight more than the specified limit (division or catch-weight) on "day of" the fight with little effects to his performance. The catch weight is not only to provide a level playing field but also to prevent weight mismatches that can endanger the fighters. And more importantly, the catch-weight is to ensure the fight is not canceled due last minute disagreement on fight time.
A case of a weight mismatch is the Arturo Gatti vs. Joey Gamache fight. In the controversial fight between Gatti vs Gamache, Gamache's handlers claimed Gatti had gained 19 pounds since the weigh-in the "day before" and thus had a large advantage over Gamache. This resulted in serious injuries to the smaller Gamache. After Gatti–Gamache, some boxing commissions started weighing boxers a second time.
Combat sports commonly have defined weight classes with specific weight limits. For example, each boxing division with the exception of heavyweight has its own limits for weight classes, ranging from 105 pounds for minimumweight to 200 pounds for cruiserweight and varying in range in the weight classes in between. In order to fight for a championship in these weight classes the fighters must come in to the fight at or below said weight.
Cases can arise when a fight does not occur within a specific weight class limit. In certain cases a contract for a fight will specify that the two fighters come into the fight at another limit. Often, this limit will be at a midpoint between two weight classes. Recent examples of catch weight fights where a weight limit was different from that of a defined weight class include the second fight between Jermain Taylor and Kelly Pavlik, which was fought at a catch weight of 166 pounds and the Félix Trinidad-Roy Jones, Jr. fight, which was fought at 171 pounds.
In another example, fighters can agree to fight at a formal weight; however, at weigh-in a fighter can come in over the formal weight. So the fight is not canceled, an agreement may be reached where the fight is made at a catch weight. Commonly, the fighter who comes in overweight pays a penalty - for example a 20% penalty with 10% going to the fighter who made weight and 10% going to a commission sanctioning the fight. An example of this catch weight situation occurred at UFC 104 where Anthony Johnson came in over the welterweight limit of 170 for his fight against Yoshiyuki Yoshida. While commissions sometimes give a one pound grace, Johnson came in at 176. An agreement was made that the fight would occur at a catch weight of 176.
Often, catch weight fights are still considered fights within a formal weight class. For example, when Manny Pacquiao fought Miguel Cotto, the fight was at a catch weight of 145 pounds to accommodate Pacquiao's smaller physique. Boxing has a junior welterweight weight class with a weight limit of 140 and a welterweight weight class with a weight limit of 147. Since the fight was under the 147 limit and above the 140 limit, the fight was considered a welterweight fight as well as being considered a catch weight fight. In addition, the World Boxing Organization sanctioned this fight for the welterweight title since the fight was under the welterweight limit.
Another example was at UFC 99 when Wanderlei Silva fought Rich Franklin at a catch weight bout of 195 pounds. Silva typically fought at the Light Heavyweight weight class of 205 pounds, while Franklin fought at the Middleweight weight class of 185 pounds. They agreed on a catch weight bout, and both men weighed in at 194 for the fight.
It should also be noted that the term 'catchweight', with the above meaning, is especially prevalent in North America; other countries may well consider catchweight to be the old wrestling meaning, when to make a contest more interesting they might have a good middleweight meeting a not-so-good heavyweight, etc.