Coin flipping Coin flipping , coin tossing , cross and pile , or heads or tails is the practice of throwing a coin in the air to choose between two alternatives , sometimes to resolve a dispute between two parties . It is a form of sortition which inherently has only two possible and equally likely outcomes . History . The historical origin of coin flipping is the interpretation of a chance outcome as the expression of divine will . Coin flipping as a game was known to the Romans as " navia aut caput " ( " ship or head " ) , as some coins had a ship on one side and the head of the emperor on the other . In England , this game was referred to as " cross and pile " . Process . During coin flipping the coin is tossed into the air such that it rotates end - over - end several times . Either beforehand or when the coin is in the air , an interested party calls " heads " or " tails " , indicating which side of the coin that party is choosing . The other party is assigned the opposite side . Depending on custom , the coin may be caught , caught and inverted , or allowed to land on the ground . When the coin comes to rest , the toss is complete and the party who called or was assigned the face - up side is declared the winner . If the outcome is unclear the toss is repeated ; for example the coin may come to rest upright against another object or fall down a drain . The coin may be any type as long as it has two distinct sides ; it need not be a coin as such . Fraudulent flipping . It is not very difficult to learn to flip a coin so as to get a reliable intended result , not by controlling the number of flips but by creating the illusion that the coin is flipping . The coin remains at a constant inclination to the vertical and simply rotates , or wobbles , about a vertical axis . The inclination must be sufficient for the coin to occupy most of the sphere that a fairly flipped coin would , while not being so great that the coin is likely to bounce when caught . An inclination around 45 degrees is usually satisfactory . Another simple way to cheat is simply to peek at the coin as it lands in your hand . Although it seems that this would be easily detectable , in fact , this can be done quickly and convincingly with some practice . The third common method of fraudulent flipping is to determine which side is up by the feel of the coin . On most USA coins , the heads side is smoother than the tails side . Three - way . Three - way coin flips are also possible , by a different process – this can be done either to choose two out of three , or to choose one out of three . To choose two out of three , three coins are flipped , and if two coins come up the same and one different , the different one loses ( is out ) , leaving two players . To choose one out of three , either reverse this ( the odd coin out is the " winner " ) , or add a regular two - way coin flip between the remaining players as a second step . Note that the three - way flip is 75 % likely to work each time it is tried ( if all coins are heads or all are tails , which occurs 1 / 4 of the time , the flip is repeated until the results differ ) , and does not require that " heads " or " tails " be called . A famous example of such a three - way coin flip ( choose two out of three ) is dramatized in " Friday Night Lights " ( originally a , subsequently film and TV series ) , where three high school football teams with identical records use a three - way coin flip – at a truck stop – to determine which two will advance to the playoffs . A legacy of this coin flip was to reduce the use of coin flips to break ties in Texas sports , instead using point - systems to reduce the frequency of ties . Use in dispute resolution . Coin tossing is a simple and unbiased way of settling a dispute or deciding between two or more arbitrary options . In a game theoretic analysis it provides even odds to both sides involved , requiring little effort and preventing the dispute from escalating into a struggle . It is used widely in sport s and other game s to decide arbitrary factors such as which side of the field a team will play from , or which side will attack or defend initially ; these decisions may tend to favor one side , or may be neutral . Factors such as wind direction , the position of the sun , and other conditions may affect the decision . In team sports it is often the captain who makes the call , while the umpire or referee usually oversees such proceedings . A competitive method may be used instead of a toss in some situations , for example in basketball the jump ball is employed , while the face - off plays a similar role in ice hockey . Coin flipping is used to decide which end of the field the teams will play to and / or which team gets first use of the ball , or similar questions in football matches , American football games , Australian rules football , volleyball , and other sports requiring such decisions . In the U . S . a specially minted coin is flipped in National Football League games ; the coin is then sent to the Pro Football Hall of Fame , and other coins of the special series minted at the same time are sold to collectors . The XFL , a short - lived American football league , attempted to avoid coin tosses by implementing a face - off style " opening scramble , " in which one player from each team tried to recover a loose football ; the team whose player recovered the ball got first choice . Because of the high rate of injury in these events , it has not achieved mainstream popularity in any football league , and coin tossing remains the method of choice in American football . In a football match , the team winning the coin toss chooses which goal to attack in the first half ; the opposing team kicks off for the first half . For the second half , the teams switch ends , and the team that won the coin toss kicks off . Coin tosses are also used to decide which team has the pick of going first or second in a penalty shoot - out . Before the introduction of the penalty shoot - out , coin tosses were occasionally needed to decide the outcome of tied matches . The most famous instance of this was the 1968 European Football Championship semi - final between Italy and the Soviet Union , which finished 0 - 0 after extra time . Italy won , and went on to become European champions . In cricket the toss is often significant , as the decision whether to bat or bowl first can influence the outcome of the game . In duels a coin toss was sometimes used to determine which combatant had the sun at his back . In some other sports , the result of the toss is less crucial and merely a way to fairly choose between two more or less equal options . The National Football League also has a coin toss for tie - breaking among teams for playoff berths and seeding , but the rules make the need for coin toss , which is random rather than competitive , very unlikely . A similar procedure breaks ties for the purposes of seeding in the NFL Draft ; these coin tosses are more common , since the tie - breaking procedure for the draft is much less elaborate than the one used for playoff seeding . Major League Baseball once conducted a series of coin flips as a contingency on the last month of its regular season to determine home teams for any potential one - game playoff games that might need to be added to the regular season . Most of these cases did not occur . From the 2009 season , the method to determine home - field advantage was changed . Fédération Internationale d ' Escrime rules use a coin toss to determine the winner of a fencing match that remains tied at the end of a " sudden death " extra minute of competition . Although in most international matches this is now done electronically by the scoring apparatus . In the United States Asa Lovejoy and Francis W . Pettygrove , who owned the claim to the land that would later become Portland , Oregon , each wanted to name the new town after their respective hometowns of Boston , Massachusetts and Portland , Maine ; Pettygrove won the coin flip . Scientists sometimes use coin flipping to determine the order in which they appear on the list of authors of scholarly paper s . Politics . Canada . In some jurisdictions , a coin is flipped to decide between two candidates who poll equal number of votes in an election , or two companies tendering equal prices for a project . For example , a coin toss decided a City of Toronto tender in 2003 for painting lines on 1 , 605 km of city streets : the bids were $ 161 , 110 . 00 ( $ 100 . 3800623 per km ) , $ 146 , 584 . 65 ( $ 91 . 33 per km , exactly ) , and two equal bids of $ 111 , 242 . 55 ( $ 69 . 31 per km , exactly ) . The numerical coincidence is somewhat less remarkable than it appears , because three of the four bids are for a whole number of cents per kilometer . Australia . In December 2006 Australian television networks Seven and Ten , which shared the broadcasting of the 2007 AFL Season , decided who would broadcast the Grand Final with the toss of a coin . Network Ten won . United Kingdom . In the United Kingdom , if a local or national election has resulted in a tie where candidates receive exactly the same number of votes after 3 recounts , then the winner can be decided either by drawing straws / lots , coin flip , or drawing a high card in pack of cards . Physics . Experimental and theoretical analysis of coin tossing has shown that the outcome is predictable , to some degree at least , if the initial conditions of the toss ( position , velocity and angular momentum ) are known . Coin tossing may be modeled as a problem in Lagrangian mechanics . The important aspects are the tumbling motion of the coin , the precession ( wobbling ) of its axis , and whether the coin bounces at the end of its trajectory . The outcome of coin flipping has been studied by Persi Diaconis and his collaborators . They have demonstrated that a mechanical coin flipper which imparts the same initial conditions for every toss has a highly predictable outcome — the phase space is fairly regular . Further , in actual flipping , people exhibit slight bias – " coin tossing is fair to two decimals but not to three . That is , typical flips show biases such as . 495 or . 503 . " In studying coin flipping , to observe the rotation speed of coin flips , Diaconis first used a strobe light and a coin with one side painted black , the other white , so that when the speed of the strobe flash equaled the rotation rate of the coin , it would appear to always show the same side . This proved difficult to use , and rotation rate was more accurately computed by attaching floss to a coin , such that it would wind around the coin – after a flip , one could count rotations by unwinding the floss , and then compute rotation rate as flips over air time . Moreover , their theoretical analysis of the physics of coin tosses predicts a slight bias for a caught coin to be caught the same way up as it was thrown , with a probability of around 0 . 51 , though a subsequent attempt to verify this experimentally gave ambiguous results . Stage magicians and gamblers , with practice , are able to greatly increase this bias , whilst still making throws which are visually indistinguishable from normal throws . Since the images on the two sides of actual coins are made of raised metal , the toss is likely to slightly favor one face or the other if the coin is allowed to roll on one edge upon landing . Coin spinning is much more likely to be biased than flipping , and conjurers trim the edges of coins so that when spun they usually land on a particular face . Counterintuitive properties . Human intuition about conditional probability is often very poor and can give rise to some seemingly surprising observations . For example , if the successive tosses of a coin are recorded as a string of " H " and " T " , then for any trial of tosses , it is twice as likely that the triplet TTH will occur before THT than after it . It is three times as likely that THH will precede HHT . ( See Penney ' s game ) Mathematics . The mathematical abstraction of the statistics of coin flipping is described by means of the Bernoulli process ; a single flip of a coin is a Bernoulli trial . In the study of statistics , coin - flipping plays the role of being an introductory example of the complexities of statistics . A commonly treated textbook topic is that of checking if a coin is fair . Coin flipping in telecommunications . There is no reliable way to use a true coin flip to settle a dispute between two parties if they cannot both see the coin — for example , over the phone . The flipping party could easily lie about the outcome of the toss . In telecommunications and cryptography , the following algorithm can be used : In lotteries . The New Zealand lottery game Big Wednesday uses a coin toss . If a player matches all 6 of their numbers , the coin toss will decide whether they win a cash jackpot ( minimum of NZ $ 25 , 000 ) or a bigger jackpot with luxury prizes ( minimum of NZ $ 2 million cash , plus value of luxury prizes . ) The coin toss is also used in determining the Second Chance winner ' s prize . Use in clarifying feelings . A technique attributed to Sigmund Freud to help in making difficult decisions is to toss a coin not actually to determine the decision , but to clarify the decision - maker ' s feelings . He explained : " I did not say you should follow blindly what the coin tells you . What I want you to do is to note what the coin indicates . Then look into your own reactions . Ask yourself : Am I pleased ? Am I disappointed ? That will help you to recognize how you really feel about the matter , deep down inside . With that as a basis , you ' ll then be ready to make up your mind and come to the right decision . " In fiction . Coin Toss ( 2012 ) an American independent film set in Chicago and Directed by Satya Kharkar . In this movie character uncle Turley an eccentric mathematics genius keeps on flipping coin to decide upon his daily tasks like whether to go for a walk or not . George Raft became famous as the coin - flipping gangster " Guino Rinaldo " in the 1932 Howard Hawks / Howard Hughes film " Scarface " ( 1932 ) . Bugs Bunny parodies Raft in the classic 1946 animated short film " Racketeer Rabbit " . Raft himself later parodied his own gangster persona as the character " Spats Colombo " in Billy Wilder ' s 1959 comedy " Some Like It Hot " : Raft sees another mobster flipping a coin and responds , " Where did you pick up that cheap trick ? " Raft ' s coin - tossing established a distinctive motif used in numerous later gangster movies . In the climax of " Sholay " , Veeru and Jaidev decide their next strategy over their encounter with the villains by tossing a coin ( they are in habit of deciding over the affairs between themselves this way ) . It is revealed at the end that the coin used by him is actually a trick coin that always come up " heads " . The 1972 movie adaptation of Graham Greene ' s novel " Travels with My Aunt " ends with a coin toss that will decide the future of one of the characters . The movie ends with the coin in mid - air , leaving their fate unresolved . The DC Comics supervillain Two - Face , ( most famously as a member of Batman ' s rogues gallery ) , has a double - headed coin with one side defaced — a parallel to his actual character , because one side of his face is deformed from acid throwing — which he relies upon for all of his decisions . He will do evil if it lands on the defaced side , and good on the other side . The coin is also representative of alter - ego Harvey Dent ' s obsession with dualism and the number 2 . In the film " The Dark Knight " , the coin starts out clean , and Harvey Dent ( played by Aaron Eckhart ) uses this trick coin to seemingly leave important decisions to chance ( " Heads I go through with it " ) . The coin is later blackened on one side in the explosion that kills his fiancée , Rachel Dawes . In " Batman Forever " , Two Face , ( portrayed by Tommy Lee Jones ) , flips his coin multiple times in one scene to see how far Bruce Wayne can come within range of his gun . After a number of tries , the scarred side finally comes up and he fires anyway . Tom Stoppard ' s " Rosencrantz & Guildenstern Are Dead " begins with a series of coin tosses that all come up heads , causing the characters to question the nature of chance and randomness . In the video game " Final Fantasy VI " brothers Edgar and Sabin flip a coin in order to determine who succeeds the throne of Figaro . It is later revealed that Edgar used a double - headed coin in order to win , allowing Sabin to live without the burden of the kingdom . This coin is also seen if Edgar is present in the first encounter with the gambler Setzer , who is highly amused by it when it is used to trick him into providing his airship . In the video game " Shenmue 2 " gang leader Wuying Ren carries a double - sided coin in each pocket , asking for a head or tail call before pulling the coin out and flipping the coin . This process guarantees him victory in the outcome of the coin toss , usually forcing protagonist Ryo into a dangerous situation . The trickery behind this method is revealed as the characters part ways at the end of the game . In " Futurama " episode The Farnsworth Parabox , Professor Farnsworth creates a parallel universe . The only difference between " our " universe and the other is that every time someone flipped a coin , it landed on the opposite side . This leads to extremely different worlds and humorous confusion . The DVD of " Final Destination 3 " has a special feature allowing the viewer to flip a coin apparently to determine the outcome of the movie ; however , the outcome is fixed to maintain the plot , and the coin flip is ignored . Isaac Asimov ' s short story " The Machine that Won the War " ends with a character revealing that he made his decisions based on coin tosses . The final episode of the American television series JAG ends with an incomplete coin flip . In the book " No Country for Old Men " ( and the film made of it ) , Anton Chigurh , the story ' s villain , occasionally flips coins for potential victims to decide whether or not to kill them . He allows people to place their life in the hands of divine providence , and those who refuse to choose are killed anyway , for their obstinacy and refusal to submit to Fate . The meaning of Chigurh ' s coin - flipping is left ambiguous ( in both the book and the film ) , and has led to considerable discussion : commentators suggest , for example , that Chigurh views himself as simply following the will of the universe , or is " merely cruel , " or that it is an inevitable outgrowth of his ( perceived ) atheism or that Chigurh is in fact a stand - in for fate , or alternatively that his adherence to chance is a way for him to deny responsibility for his actions or to displace that responsibility onto his victims . In the manga / anime of Hunter x Hunter by Yoshihiro Togashi , a servant of the Zaolydeck family challenges Gon and his companions , Leorio and Kurapica , to a game involving a coin flip . The game is simple : Yoshihiro flips the coin in the air and quickly snatches it before the coin falls , then Gon or his companions have to say which hand the employee caught the coin with . This proves to be incredibly difficult due to the unrealistic speed of the coin flipper ' s hands . Gon is very observant and is occasionally able to guess right . " See " Flipism . In The Mentalist episode " Blood In , Blood Out " during season 2 , CBI consultant Patrick Jane wins a wager by flipping a coin and it landing on heads 20 times in a row . It is later shown that he rigged the coin in his favor . Coin landing on its edge in fiction . A coin toss has a theoretical third outcome , in which the coin comes to rest upright on its edge , rather than falling to either heads or tails . Such an outcome is nearly impossible in reality , but is seen in fiction , often for comedic effect . Such an outcome usually results in either a tied coin toss , or victory to a person who successfully called " edge " . In the 1939 film " Mr . Smith Goes to Washington " , a state governor has to select an interim Senator , and he is being pressured by two opposing factions to choose between their respective candidates , Mr . Hill and Mr . Miller . Unable to choose , he flips a coin in the privacy of his office , but it falls against a book and lands on edge . Consequently , he makes neither choice and chooses Mr . Smith . In " The Twilight Zone " episode " A Penny for Your Thoughts , " the main character buys a newspaper , and flips a coin into the collection pan , where it lands on its edge . As a consequence , he can hear people ' s thoughts , but at the end of the day he knocks the coin off its edge when dropping another coin into the pan , which causes him to lose his telepathic ability . In the American comedy film " Mouse Hunt " , out - of - work brothers Lars and Ernie toss a coin to decide who gets to sleep in the only bed in the inherited house . The coin ends up spinning on the floor and coming to rest on edge , so the brothers share the bed . The Hong Kong - made film " Shaolin Soccer " contains a scene in which one of Sing ' s brothers is being asked to join Sing ' s soccer team , and he refuses because he mathematically predicts the team will fail ; he uses a coin toss to demonstrate his point , saying it has zero chance of landing on its edge . When the coin is carelessly dropped later in the scene , the brother is amazed to discover that it has , indeed , landed on its edge and become stuck inside a small crack in the asphalt . In an episode of Malcolm in the Middle , Malcolm decides to flip a coin in order to resolve a dispute about keeping a potentially offensive cardboard cut - out up in the store that he works in ( citing that logic wasn ' t good enough ) . The coin is shown to land on its edge , leaving Malcolm uncertain what to do . In Scrubs episode " " My Best Friend ' s Baby ' s Baby and My Baby ' s Baby " " , protagonist J . D . and Kim cannot decide whether or not to keep their baby after an accidental pregnancy . When all else fails , they flip a coin , which lands on its edge . In How I Met Your Mother episode " Blitzgiving " , Steve Henry flipped a coin just as Barney left the room . The coin landed on its side and remained there until Barney returned . In The Simpsons episode " Waverly Hills 9 - 0 - 2 - 1 - D ' oh " , A city inspector asks Homer to call a coin toss , to which Homer calls as the last moment as side , proving to be correct . In the video game Soul Reaver 2 , Kain proposes the possibility of a coin landing on its edge when discussing a fateful outcome critical to plot development .