<P> Goalposts are located at the center of the plane of each of the two end lines . The crossbar of these posts is ten feet (3.0 meters) above the ground, with vertical uprights at the end of the crossbar 18 feet 6 inches (5.64 m) apart for professional and collegiate play and 23 feet 4 inches (7.11 m) apart for high school play . The uprights extend vertically 35 feet on professional fields, a minimum of 10 yards on college fields, and a minimum of ten feet on high school fields . Goal posts are padded at the base, and orange ribbons are normally placed at the tip of each upright . </P> <P> The football itself is an oval ball, similar to the balls used in rugby or Australian rules football . At all levels of play, the football is inflated to ​ 12 ⁄ to ​ 13 ⁄ pounds per square inch (psi) and weighs 14 to 15 ounces (397 to 425 grams); beyond that, the exact dimensions vary slightly . In professional play the ball has a long axis of 11 to ​ 11 ⁄ inches, a long circumference of 28 to ​ 28 ⁄ inches, and a short circumference of 21 to ​ 21 ⁄ inches, while in college and high school play the ball has a long axis of ​ 10 ⁄ to ​ 11 ⁄ inches, a long circumference of ​ 27 ⁄ to ​ 28 ⁄ inches, and a short circumference of ​ 20 ⁄ to ​ 21 ⁄ inches . </P> <P> Football games last for a total of 60 minutes in professional and college play and are divided into two - halves of 30 minutes and four - quarters of 15 minutes . High school football games are 48 minutes in length with two - halves of 24 minutes and four - quarters of 12 minutes . The two - halves are separated by a halftime period, and the first and third quarters are also followed by a short break . Prior to the start of the game, the referee and team captains for each team meet at midfield for a coin toss . The visiting team is allowed to call' heads' or' tails'; the winner of the toss is allowed to decide between choosing whether to receive or kick off the ball or choosing which goal they want to defend, but they can also defer their choice until the second half . The losing team, unless the winning team decides to defer, is allowed to choose the option the winning team did not select, and receives the option to receive, kick, or select a goal to defend to begin the second half . Most teams choose to receive or defer, because choosing to kick the ball to start the game would allow the other team to choose which goal to defend . Teams switch goals following the first and third quarters . If a down is in progress when a quarter ends, play continues until the down is completed . </P> <P> Games last longer than their defined length due to play stoppages--the average NFL game lasts slightly over three hours . Time in a football game is measured by the game clock . An operator is responsible for starting, stopping and operating the game clock based on the direction of the appropriate official . A separate clock, the play clock, is used to determine if a delay of game infraction has been committed . If the play clock expires before the ball has been snapped or free - kicked, a delay of game foul is called on the offense . The play clock is set to 40 seconds in professional and college football and to 25 seconds in high school play or following certain administrative stoppages in the former levels of play . </P>

How long is a quarter in a nfl football game