Estimation is a game for 4 players in which the standard international 52card pack is used. The game is normally played counterclockwise. The objective of the game is for players to try to estimate the number of tricks they can get in each round. The game ends after round 18.
Cards and Dealing
13 cards are dealt to each player, the cards in each suit ranking from low to high: 2  3  4  5  6  7  8  9  10  J  Q  K  A.
Bidding
The bidding is split into 2 types: normal bidding and fast bidding. Normal bidding is used in the first 13 rounds of the game, and fast bidding is used in the last 5 rounds.

Normal Bidding:
 Bidding starts with the game creator and moves counterclockwise. If a player lacks one suit (or more), they have to either choose to redeal the cards or declare an "Avoid".
 Players bid in turn according to the estimated number of tricks they think they can get, or declare a "Dash Call", which means that the estimated number of tricks is zero. Players have to declare their trump suit along with their bid.
 The winner of the bidding round is the player who estimates the highest number of tricks. In case of a tie, the trump suit is used to determine the winner. The suits are ranked from high to low: No Trump (NT), Spades, Hearts, Diamonds, Clubs. After the winner is determined, players are given a chance to estimate the number of tricks they will get based on the trump suit that was selected. The maximum number of tricks a player can estimate is the number estimated by the winner of the bidding round.

Fast Bidding
Rounds 14, 15, 16, 17, and 18 are accelerated rounds during which players are only asked to declare "Avoid" (if applicable) then sent straight to estimation (i.e. no bidding). Trump suits are predetermined in these rounds:
 Round 14 : No Trump (NT)
 Round 15 : Spades
 Round 16 : Hearts
 Round 17 : Diamonds
 Round 18 : Clubs
Notes
 If a player estimates 0 tricks in the estimation round, it's called a "Dash".
 No more than 2 players can declare a "Dash Call" or a "Dash" in any given round.
 The total number of estimated tricks CANNOT equal 13. This means that the last person to estimate (called the "Risk" or "Double Risk") is not shown the number that would make the total estimated tricks equal to 13.
 If a player estimates the same number as the winning bid, they are labeled as "With".
Play
 The winner of the bidding round leads the first trick and players must follow suit. Each trick is won by the highest card and the winner of each trick leads the next.
 Players unable to follow it have the option to use "trump" cards, which are considered the highest among other cards. The winner of the trick is the player who uses a trump, unless a higher trump is used.
 The round ends when players are out of cards.
 If no players win (i.e. no one gets their estimated number of tricks) then no scores are added and players move to the next round in which the score is doubled (called "Sa'aydeh" round).
Scoring
Players who get the EXACT same number of tricks as they estimated are considered winners. Points are calculated based on the following rules:
 Main points (X): the number of tricks estimated by the player is added to their score if they won. The difference between the number estimated and the number of tricks taken is subtracted from their score if they lost.

Extra points (Y)
 Player won the bidding round: 20 points (win), 10 points (loss).
 Dash Call: 23 points (win), 23 points (loss).
 Regular player: 10 points (win), 0 points (loss).
 Risk: 20 points (win), 10 points (loss).
 Double Risk: 30 points (win), 20 points (loss).
 With: 20 points (win), 10 points (loss).
 With Risk: 30 points (win), 20 points (loss).
 With Double Risk: 40 points (win), 30 points (loss).
 10 points are added if the player is the only one to win in the round, 10 points are subtracted if the player is the only one to lose in the round.
 If the total number of estimates is less than 13 and the player estimates 0 tricks, 10 points are added if they win, 10 points are subtracted if they lose.
 Bidding multiplier (Z): 1 if the player estimates 7 tricks or less, 2 if the player estimates 8 or more.
 Round multiplier (W): 1 unless it's a "Sa'aydeh" round
 Player points: (X + Y) * Z + (X + Y) * (W  1) + (X + Y) * (Z  1) * (W  1)
 At the end of the game, the player with the highest number of points wins.