Illegal Formations in Football - Definition and Explanation

Line of scrimmage
New York Giants v New York Jets.

 Al Pereira / Getty Images

An illegal formation is a penalty that is called against the offense for failing to line up prior to the snap according to specific guidelines.

Illegal Formations

There are several different ways for an offense to improperly line up that can result in an illegal formation call:

Having fewer than seven players line up on the line of scrimmage results in an illegal formation penalty. A total of at least seven players must always line up on the line of scrimmage prior to the play. Along with the offensive linemen, tight ends and receivers usually make up the initial seven on the line. The seven players must remain on the line until the ball is snapped.

Having eligible receivers who do not line up as the leftmost and rightmost players on the line also results in an illegal formation penalty. Eligible receivers must always be the furthest players to line up on each side of the line of scrimmage. Thus, a wide receiver cannot line up in the middle of the offensive line and then break out to receive a pass.

Traditional Formation 

WR G T C T G TE WR         




As you can see, there are eight players lined up on the line of scrimmage in this situation: A wide receiver to the left of the line, two guards, two tackles, a center, a tight end, and a wide receiver to the right. Both of the receivers are the furthest players lined up to each side of the line.

Lined up behind the line of scrimmage is the quarterback, who lines up behind, and receives the snap from the center, and two different backs; a fullback and a running back. This is a legal formation.

An illegal formation would have only six players on the line of scrimmage, potentially with the receiver lined up behind it. 

In this situation, only six players are lined up on the line of scrimmage: A wide receiver, two guards, two tackles, and a center. In addition to the quarterback, fullback, and running back, the tight end and second wide receiver are both lined up slightly behind the line of scrimmage. This is an illegal formation, as there aren’t the required seven offensive players lined up on the line of scrimmage. If the receiver bumps up to the line of scrimmage, the formation would then be legal.                            

Lastly, five properly numbered ineligible players failing to line up on the line results in an illegal formation penalty. Teams have to have at least five guys on the line of scrimmage wearing a number between 50 and 79. Teams can have more than five players on the line wearing such numbers, but they cannot have fewer than five.

An illegal formation results in a five-yard penalty against the offending team.