Canasta Basic Scoring
Canasta is a complex game; while the rules are simple enough, there is a great deal of strategy involved in becoming a solid player. The details of scoring are straight-forward, but novice players may overlook several things that could be played to their advantage. In Canasta, the game is over when you meld out, but you want to make sure that you never do so while your opponent is ahead in points, so paying close attention to the scoring as you go is crucial to securing a win in this game.
The first step in understanding Canasta scoring is knowing how the red threes work. Because a Canasta deck is typically comprised of two decks of cards with jokers, there are four red threes. Each red three is worth 100 points, and if you have all four, their value is doubled (for 800 points for all four). The added bonus from having all four red threes is substantial, and if your opponent has yet to find any red threes, you would do well to keep playing in hopes of finding the remainder and getting the bonus. This is a particularly useful tactic if you're neck and neck in terms of points from melds. Be warned, however, that if you haven't made any melds when the other person or team melds out, you will be penalized for the red threes that you have (any points that you would have earned from the red threes will be subtracted from your score instead).
Scoring melds in canasta is fairly simple, as melds are scored either by the value of the card or as canastas (a meld of seven or more of the same kind of card). There are two kinds of canastas-- natural melds and mixed melds. Natural melds are made up only of the card itself, with no wilds. A natural canasta of queens, for instance, would be made up of seven queens. Mixed canastas are far more common, as there are only eight of any one type of card in the canasta deck. Mixed canastas are made up of a blend of the card and wild cards (twos and jacks), with the card in question outnumbering the wild cards. Each natural canasta is worth 500 points, and each mixed canasta is worth 300. Cards that are melded but not in canastas have the following values: black threes and cards 4-7 are worth 5 points each, 8-K are worth 10 points each, 2s and As are worth 20 each, and Jokers are worth 50 points each.
Other Ways to Score
In addition to the points from red threes and melds, there are two other scoring points worth mentioning. The cards remaining in the hand of the player(s) who have not melded out will be subtracted from their total at the end of the hand, and the player(s) who meld out will gain an extra 100 points. All in all, an extra 100 points is not a large amount, so be sure to make sure that you're not melding out just to get the jump on your opponent-- the first trick of canasta is knowing the best time to play your last cards.