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 a matter of style, tradition and semantics.
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. The numbers used relate to the player's primary position when they are first assigned a number. If they later change positions, they can keep their prior number, unless it conflicts with the eligible receiver rule; that is only players that change positions from an eligible position (such as receiver or back) to an ineligible position (such as an offensive lineman) are required to change numbers if they change position. Additionally, during a game a player may play out-of-position, but only after reporting in to the referees, who will announce to the stadium that a specific player number has reported in (for example "Number 61 has reported as an eligible receiver") to alert the opposing team, other officials, and the audience that a player is legally out-of-position.
Although the NFL does allow teams to retire jersey numbers, the league officially discourages the practice for fear of teams running out of numbers; the rule book requires teams to make available retired numbers for new players should they exhaust all available numbers at a particular position.
According to NCAA rule book, Rule 1 Section 4 Article 1 "strongly 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.
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.