This constant represents the NFL's minimum length of a football and is defined to be no less than `11` inches.¹

Since we can approximate the shape of a football with an ellipsoid the image shows that the length of the football is twice axis `a`.

See also

• Ohio State vs Michigan Scores
• Football Calculator
• Aerodynamic Torque on a Football
• Deflection Due to Magnus Force
• Drag Force on a Football
• College Football Consensus National Champions Data
• Most College Championships
• Number of College Football Championships
• Goal Post Cross-bar Height (American Football)
• Length of Football Field
• Sport Ball Sizes
• Minimum Football Circumference - NCAA
• Minimum Football Length - NCAA
• Maximum Football Circumference - NCAA
• Maximum Football Length - NCAA
• Minimum Football axis_1 or axis_2 - NCAA
• Maximum Football axis_1 or axis_2 - NCAA

1. ^ 2015 NCAA Football Rules and Interpretations