Every football player's uniform has a number on it that is unique for that particular team, making it simpler for fans, coaches, announcers, and officials to differentiate between players. On April 5, 1973, a jersey-numbering system was adopted by the NFL where each position on the football field is given a range of numbers for each player at that position to choose from, however, there are a few players around the league that are exceptions to the rule. This chart explains which number ranges are assigned to each position.
1-9 Quarterbacks and Kickers
10-19 Quarterbacks, Receivers, Tight Ends, and Kickers
20-49 Running Backs and Defensive Backs
50-59 Centers and Linebackers
60-79 Defensive Linemen and Offensive Linemen
80-89 Receivers and Tight Ends (or 40-49 if those ranges are taken)
90-99 Defensive Linemen and Linebackers