Uniform number (American football)
Uniform numbers in American football are unusual compared to those in other sports. They are displayed in more locations on the uniform; they are universally worn on both the front and back of the jersey; and in many cases "TV numbers" are displayed on either the jersey sleeves, the shoulder pad, or occasionally on the helmets. The numbers on the front and back of the jersey also are very large, covering most of the jersey. More important, certain numbers may only be worn by players playing specific positions; thus, the jersey numbers assist the officials in determining possible rules infractions by players.
Under current rules in all three of the most prominent levels of American football (high school football, college football and professional football), all players must wear a number from 1 to 99, and no two players on the same team may wear the same number on the field at the same time. In the past, players have used the numbers 0, 00 and, in two special cases, 100. Those who wear numbers from 50 to 79 are, by rule, playing in specific positions which are prohibited from catching or touching forward passes if their team is in possession of the ball, unless explicitly indicated to the referee during a tackle-eligible play. Other than this, the correspondence between jersey numbers and player positions is largely an issue of semantics.
National Football League
The National Football League numbering system dates from a large scale change of their rules in 1973, subsequently amended in various minor ways. As of 2015, players are generally required to wear numbers within ranges based on their positions as shown in the following table.
|Number Range||QB||RB/FB||WR||TE / H||OL||DL||LB||DB||K / P|
Long snappers, not listed in the league's numbering system, can wear any number from 40 to 99; as the long snapper is seldom listed as a distinct position, players who long-snap are often listed as backup centers or backup tight ends.
Exceptions to this system do exist, including during the National Football League preseason with associated larger team rosters. A notable exception is that wide receivers can wear single-digit numbers. The numbers used relate to the player's primary position - unless it conflicts with the eligible receiver rule, players whose primary position changes during a season, do not need to change their number.
Although the NFL does allow teams to retire jersey numbers, the league officially discourages the practice for fear of teams running out of numbers. As a result, a few teams do not retire jersey numbers.
According to NCAA rule book, Rule 1 Section 4 Article 1 recommends numbering as follows for offensive players:
Otherwise all players must be numbered 1–99; the NCAA makes no stipulation on defensive players. Two players may also share the same number though they may not play during the same down.
The lowest numbers are often considered the most prestigious, and they are frequently worn not just by specialists and quarterbacks but also by running backs, defensive backs, and linebackers. Kickers and punters are frequently numbered in the 40s or 90s, which are the least in-demand numbers on a college roster. The increased flexibility in numbering of NCAA rosters is needed since NCAA rules allow larger rosters than the NFL; thus teams would frequently exhaust the available numbers for a position under the NFL rules. It is not uncommon for NCAA teams to have duplicate numbers, with an offensive player having the same number as a defensive one—this is allowed as long as both players are not on the field at the same time. Usually, one of the players will be a reserve who rarely plays, but this is not always the case: for example, the 2005 Texas Longhorns team had two key players who both wore #4: wide receiver Limas Sweed and linebacker Drew Kelson. The 2007 USC Trojans team had two key players who both wore #10: quarterback John David Booty and linebacker Brian Cushing. The 2008 Missouri Tigers both had key players wearing #1: safety William Moore and running back Jimmy Jackson. In the same season, the Alabama Crimson Tide had four numbers shared by two players each. In the 2009 season, the Ohio State Buckeyes roster also had numerous duplicate numbers: quarterback Terrelle Pryor and cornerback Malcolm Jenkins both wore #2, and running back Daniel Herron and linebacker Marcus Freeman both wore #1, while USC had both running back C. J. Gable and safety Taylor Mays wearing #2. At Texas, both safety Earl Thomas and quarterback Colt McCoy both wore #12. In 2010 at the University of Illinois, both quarterback Nathan Scheelhaase and linebacker Martez Wilson wore #2. In 2012, Notre Dame starting linebacker and team captain Manti Te'o and starting quarterback Everett Golson both wore #5. Virginia Tech defensive end Ken Ekanem wore #4 from 2013 through 2016, sharing the number with running back JC Coleman in 2013-2015 and quarterback Jerod Evans in 2016. For the 2016 Michigan Wolverines both starting quarterback Wilton Speight and defensive tackle Rashan Gary wore #3.
Perhaps the most interesting use of duplicate numbers was at South Carolina. Both cornerback Stephon Gilmore and quarterback Stephen Garcia wore #5. However, Gilmore also played quarterback for the Gamecocks, usually in the wildcat formation. During the annual end of season derby in 2009, Head Coach Steve Spurrier effectively rotated Garcia and Gilmore at the quarterback position, confusing the Clemson defense (and many fans). Because Garcia and Gilmore were never on the field at the same time, it was perfectly legal.
Individual schools often have superstitions or traditions involving certain numbers. It may be a great honor to be given the number 1 uniform, for example, such as at the University of Michigan. The top-performing walk-on at Texas A&M University will often be issued number 12, in reference to their 12th Man tradition. Syracuse University historically reserved number 44 for its best running backs, including Jim Brown, Ernie Davis, and Floyd Little, finally retiring the number permanently in 2005. The number 12 is also prestigious at the University of Alabama. It is usually reserved for top quarterbacks, although it was worn by 1930s lineman Bear Bryant, who became a coaching legend at Alabama. Since Bryant's era, it has been worn by Kenny Stabler, Joe Namath, Brodie Croyle, and Greg McElroy. At Ole Miss, the #38 worn by defensive back Chucky Mullins, who suffered a paralyzing injury in a 1989 game that ultimately led to his death in 1991, was given each season as an award to a defensive player who was seen as epitomizing Mullins' spirit. The number was retired in Mullins' memory in 2006, but it was an unpopular move, and the number as award was restored in 2010 with both offensive and defensive players eligible to win the award now. Beginning in 2016, Virginia Tech head coach Justin Fuente began awarding the team's top special teams player with the number 25 on a weekly basis in honor of the recently retired Frank Beamer (the number Beamer wore in his playing days at Virginia Tech).
Another notable exception was during the 1963 season at West Virginia University; the college was able to successfully lobby the NCAA to allow a player, namely kicker Chuck Kinder, to wear the jersey Number 100 for the state's 100th anniversary. Kinder continued to wear this jersey until the 1966 season, when the new coaching staff asked him to stop wearing it due to all the questions they were receiving about the unusual number. Similarly, University of Kansas kicker, Bill Bell, and University of Louisville defensive back, Mike Detenber, each wore jersey number 100 in 1969 as part of the celebration of the 100th anniversary of college football.
In 2013, Michigan quarterback Devin Gardner was given jersey number 98 to wear as part of the Michigan Football Legends program. Before 2011, the number had been retired in honor of Tom Harmon, a Michigan legend and the father of actor Mark Harmon. Although it is unusual for a quarterback to wear a number higher than the 20s even at the collegiate level, Gardner, a redshirt junior at Michigan, wore the number for the remainder of his career at Michigan. He wore number 12 (a more standard number for a quarterback) before being honored.
On high school and other lower youth teams, jerseys with different number ranges are different sizes, and since many of these teams do not reorder jerseys every year, players are often assigned numbers based more on jerseys that fit them rather than specific position. Odessa Permian High School (of Friday Night Lights fame) plays in Texas, where NCAA rules are used; yet Permian's tradition is that quarterbacks will wear numbers in the 20s unlike most schools in college or high school. 
Although previous editions of the National Federation of State High School Associations rule book indicated a recommended numbering system nearly identical to the NCAA's, later editions from approximately 2000 onward only indicate the bare minimum requirements: offensive linemen must be numbered from 50 to 79, while backs and ends must wear numbers either from 1 to 49 or 80 to 99.
- Only centers are permitted to wear these numbers, but there have been exceptions. For instance, guard Brian Waters wore No. 54 for all but one season of his career. Since 2010's, however, offensive guards can also wear numbers in the 50's. Connor Williams wears no. 52 after being drafted as a guard by Dallas Cowboys in 2018.
- 2015 NFL Rulebook
- Ty Montgomery [@TyMontgomery2] (11 March 2017). "Me and Rod Bernstine have something in common.... and it's not #88 #keepingit" (Tweet) – via Twitter.
- Rapoport, Ian (September 8, 2008). "What's the deal with duplicate numbers?". Birmingham News. Retrieved September 27, 2008.
- "The Legend of #44". Syracuse University Athletics. Retrieved February 19, 2007.
- Stallard, Mark (2004). Tales from the Jayhawk Gridiron. Sports Publishing. The anecdote featuring Bell's number 100, with a picture of Bell's number 100 jersey, can be found on pages 94–96.
- Hinnen, Jerry (September 7, 2013). "Devin Gardner to wear No. 98 in honor of Tom Harmon". CBS Sports.
- "Permian blasts Timon (NY)". September 16, 2006. Retrieved November 12, 2017.