Overview

There are three curling events: the men’s tournament and the women’s tournament, which are identical in format, and mixed doubles. A men’s tournament was contested at the inaugural Olympic Winter Games in 1924, but the IOC did not officially recognize the results of that tournament until 2006. The men’s tournament returned to the Olympic program at the 1998 Nagano Games, while the women’s event appeared for the first time the same year. Mixed doubles curling made its Olympic debut in 2018.

Men's and women's curling teams deliver the stones in a set order, which is presented to the officials before the game. Games in the men's and women's tournaments consist of 10 ends, eight ends in mixed doubles (an end is similar to a baseball inning).

During each end of traditional curling, teams deliver eight stones, two stones per person. Each end starts with the leads alternating throws until each has thrown their two stones. They are followed by the seconds in the same manner, and so on. The order of the lineup may not be changed during the game. 

Mixed doubles teams play five stones each and start every end with one stone that has been pre-placed, so the maximum amount of points in each end is six. During each end, one player delivers stones one and five. The other player delivers stones two, three and four. Both players are allowed to switch playing positions between ends.

The score for the end is determined when all stones have been delivered. The team that scores points during an end shoots first in the next end.

Shooting last is described as “having the hammer.” If neither team scores, the team that shot last in the end, shoots last again in the next end.

How to win in curling

The team with the most points after all ends is the winner.

During the round robin, a team may concede the game once a minimum of six ends have been completed. During the playoffs, a minimum of eight ends must be completed. Conceding the game when the losing skip feels they are too far behind to come back is fairly common and is an accepted part of the sport's etiquette.

If the game is tied after regulation, extra ends are played until a team scores more than their opponent in a single end, resulting in a winner.

The Spirit of Curling

Referenced in the first line of the World Curling rules, curlers honor the "Spirit of Curling," which dictates the moral rules for athletes during a curling match. It reads:

"Curling is a game of skill and of tradition. A shot well executed is a delight to see and it is also a fine thing to observe the time-honoured traditions of curling being applied in the true spirit of the game. Curlers play to win, but never to humble their opponents. A true curler never attempts to distract opponents, nor to prevent them from playing their best, and would prefer to lose rather than to win unfairly. Curlers never knowingly break a rule of the game, nor disrespect any of its traditions. Should they become aware that this has been done inadvertently, they will be the first to divulge the breach. While the main object of the game of curling is to determine the relative skill of the players, the spirit of curling demands good sportsmanship, kindly feeling and honourable conduct. This spirit should influence both the interpretation and the application of the rules of the game and also the conduct of all participants on and off the ice."

Curling button

The center of the circles is known as the tee, which also can be referred to as the “button.” A team scores a point for each stone that is closer to the button than the opponents’ best stone, provided that the stone is within 1.83 meters (6 feet) of the tee. This circular area is known as the house; it is the scoring zone in curling.

Curling playing surface

The playing surface in curling is 45.72 meters (150 feet) long and five meters (16 feet, five inches) wide. The ice is set up to accommodate play in both directions, meaning the surface is symmetrical with a house at each end.

The house

The house is four concentric circles, with the outer edge of the outer circle having a radius of 1.829 meters (six feet), the next circle a radius of four feet, the next circle a radius of 610 millimeters (two feet), and the innermost circle having a minimum radius of 152 millimeters (six inches). This outside circle marks the edge of the house.

Players start a stone moving from a rubber block called the hack. Players push off from the back and begin sliding forward, guiding the stone along the ice. Players must release the stone before the front edge touches the hog line, which is 10.05 meters (33 feet) from the hack and 28.34 meters (93 feet) from the tee line at the other end. 

At the rear edge of each house is the back line.  It is located six feet from the tee line.

Free Guard Zone

The area between the hog line and the tee line, excluding the house, is known as the free guard zone. No stone in this area may be removed from play by the opposition until the first four stones in an end have come to rest. Players are allowed to bump other stones with shots, but are not allowed to knock a stone out of play. 

Any shot played when the free guard zone rule is in effect that results in an opposition stone being knocked out of play is an infraction. In this case, the played stone is removed from play and any other stone that was moved is replaced. For any stone lying within the house, normal rules apply at all times.
    
This rule was enacted in 1991 to hinder defense-oriented play. In the past, teams would knock out one another’s rocks repeatedly, resulting in low-scoring games that were boring to many spectators. 

There is no free guard zone in mixed doubles curling (see below for additional details on mixed doubles curling rules).

Sweeping

After a stone is thrown, players are allowed to sweep the ice in front of the stone. Sweeping clears the ice of any debris that might slow the stone down or send it off course. Sweeping also melts a thin layer of ice that reduces friction and thus increases the distance the rock travels. 
    
Sweeping is allowed by any player on the throwing team between the two tee lines. Players are not allowed to sweep opponents' stones in that area. 

Behind the tee line at the playing end, only one player from each team may sweep at any one time. This may be any player of the delivering team, but only the skip or vice-skip (third) of the non-delivering team.

Only stones in motion – termed “running stones” – may be swept. Players may not touch any stones while sweeping. Also, they may only sweep in front of the stone, in a direction perpendicular to the direction of motion.

Players are allowed to sweep stones that are set in motion by other stones.

Game timing

Men's and women's teams have a total of 38 minutes of thinking time for a 10-end game. In addition, each team may call one 60-second timeout during each game to consult with its coach. Each team's clock begins after the opposing team's shot is considered complete and stops once the next stone is delivered. The time must be displayed on a clock clearly visible to the players. If a team’s clock runs out before the completion of the game, the team forfeits the game. Mixed doubles teams receive 22 minutes of thinking. There is a five-minute break after the completion of the fourth end in mixed doubles and the fifth end in men's and women's.

Curling extra end rules

If a game requires an extra end or ends, men's and women's teams receive four minutes and 30 seconds of thinking time for each extra end. There will be one-minute breaks between the 10th and 11th end and any subsequent ends. Each team can call one 60-second timeout in each extra end. When extra ends are required in mixed doubles, each team shall receive three minutes of thinking time for each extra end.

Player substitution

If a player is injured and cannot continue to play, or cannot start the game, the team has two choices. One is to continue the game with only three players, with the first and second player in the lineup each throwing three stones. The second is to insert the alternate into the missing players' spot at the start of the next end. The playing rotation can be changed when a substitute enters the game. Mixed doubles teams are not permitted a substitute.

Touching a moving stone

Between the tee line at the delivering end and the hog line at the playing end: If a moving stone is touched, or is caused to be touched, by the team to which it belongs, or by their equipment, the touched stone is removed from play immediately by that team. A double touch by the person delivering the stone, before the hog line at the delivering end, is not considered a violation. If a moving stone is touched, or is caused to be touched, by an opposition team, or by its equipment, or is affected by an external force: 

1. If the stone was the delivered stone, it is delivered
2. If the stone was not the delivered stone, it is placed where the team to which it belongs reasonably considers it would have come to rest had it not been touched

Inside the hog line at the playing end: If a moving stone is touched, or is caused to be touched, by the team to which it belongs, or by its equipment, all stones are allowed to come to rest, after which the non-offending team has the option to: 

1. Remove the touched stone, and replace all stones that were displaced after the infraction to their positions before the violation took place
2. Leave all stones where they came to rest
3. Place all stones where it is reasonably considered the stones would have come to rest had the moving stone not been touched

Touching a stationary stone: If a stationary stone, which would not have affected the outcome of a moving stone, is displaced, or caused to be displaced, by a player, it is replaced by the non-offending team to the positions before the violation taking place. 

If a stationary stone, which would have had no effect on the outcome of a moving stone is displaced, or caused to be displaced, by an external force, it is replaced, with agreement of the teams, to its position before the violation took place. 

If a stone that would have altered the course of a moving stone is displaced, or caused to be displaced, by a player, all stones are allowed to come to rest and then the non-offending team has the option to: 

1. Leave all stones where they came to rest
2. Remove from play the stone whose course would have been altered, and replace any stones that were displaced after the violation to their positions before the violation took place
3. Place all stones in the positions the team reasonably considers they would have come to rest had a stone not been displaced

If a stone that would have altered the course of a moving stone is displaced, or caused to be displaced, by an external force, all stones are allowed to come to rest, and are then placed in the positions in which they would have come to rest had a stone not been displaced. If the teams cannot agree, the stone is redelivered after all displaced stones have been replaced to their positions prior to the violation taking place. If agreement on those positions cannot be reached, the end is replayed. 

If a displacement is caused by stones deflecting off the sheet dividers, the stones are replaced, by the non-delivering team, to their positions prior to the violation taking place.

Playing out of order: If a player delivers a stone out of proper rotation, the end continues as if the mistake had not occurred. The player who missed a turn delivers the last stone for that team in that end. If it cannot be determined which player delivered out of proper rotation, the player who delivered the first stone in the end for that team delivers the last stone for that team in that end.

Incorrect sweeping: If a stone is swept improperly by a team, the non-offending team has the option of allowing the play to stand, or of placing the stone, and all stones it would have affected, where they would have come to rest had the violation not occurred.

If a player releases a stone after it has touched the hogline, a violation is called and the stone is removed from play. If the stone has hit another stone, all affected stones are put back to their original location.

Per World Curling rules, questions about the rules are adjudicated by an umpire, unless there is an appeal against an umpire's decision, in which a decision of the chief umpire is final say.

While disqualifications are rare in curling, there are some instances where teams can be disqualified in a curling match.

Prohibited substances: If a player uses performance-enhancing drugs without therapeutic exemption in curling, the player will be disqualified and could lead to further suspension in international competition.

Equipment violation: If a player violates the Statement of Principles for Competition Equipment, penalties include:

Inappropriate behavior: Improper conduct, foul or offensive language, equipment abuse or willful damage on the part of any team member can result in suspension. During a match, a chief umpire reserves the right to disqualify a team for unsportsmanlike behavior, which earns the team a DQB.

Per World Curling rules, "The chief umpire may eject a player, coach or team official from a game for what is considered to be unacceptable conduct or language. The ejected person must leave the competition area and take no further part in that game. When a player is ejected from a game, an alternate player may not be used in that game, for that player."

There is no free guard zone in mixed doubles curling, which is the area in men’s and women’s curling from the hogline to the tee line (excluding the front half of the house) where an opposition stone cannot be removed out of play until the sixth stone has been thrown (the third hammer stone). Instead, no stone may be removed from play - both team stones and opposition stones - until the fourth stone (second hammer stone) is thrown.

Positioned stones in mixed doubles curling

Before the start of every end, one team shall place their team’s “positioned” stone at the playing end of the sheet in one of two positions, designated A, and the opponent’s “positioned” stone then shall be placed in whichever position (A or B) remains vacant. The location of these positions shall be as follows:

Position A: Placement so that the stone is bisected by the center line and either is immediately in front of or immediately behind one of 3 points in the ice. The points are placed on the center line:

1. At the mid-point between the hog line and the outermost edge of the top of the house
2. 0.915 meters (3 feet) from the mid-point closer to the house
3. 0.915 meters (3 feet) from the mid-point closer to the hog

Based on the ice conditions, the chief umpire shall determine the specific placement for Position A to be used before the start of the pre-game practice, and that same placement must be used for the entire game.

(b) Position B: Placement so that the stone is bisected by the center line and is in the back of the 4-foot circle. The back edge of the stone is aligned with the back edge of the 4-foot circle.

Curling Power Play Rules

Once per game, each team, when they have the decision on the placement of the “positioned” stones, can use the “Power Play” option to position the stones. The Power Play option cannot be used in extra ends.

(a) The in-house stone, which belongs to the team with the last stone in that end, is placed with the back edge of the stone abutting the front edge of the tee line, with half the stone in the 8-foot circle and half in the 12-foot circle.

(b) The guard stone is positioned to the side of the sheet, so it would be bisected by a direct line between the middle of the in-house stone to the middle of the hack. The distance of this corner guard from the house is the same distance that was determined for the center guards.