Calculation is a solitaire card game. It offers more scope for skill than many similar games; it is sometimes said that a skilled player can win Calculation three times out of five.

At the start of play, one ace, deuce, three, and four of any suit are removed from a standard deck of cards and laid out as the foundations. The ace foundation is to be built up in sequence until the king is reached, disregarding suit. The other foundations are similarly built up, but by twos, threes, and fours, respectively, until they each reach a king, as in the following table:

The tableau, initially empty, consists of four piles of cards, usually arranged immediately below the four foundations.

Play in Calculation is simple. A single card is turned up from the stock and played either to the top of any of the four tableau piles, or, if desired and possible, onto one of the foundations. The top card of any tableau pile may also be played onto one of the foundation piles if it is the next number in the appropriate sequence for that foundation. The game is won when all cards have been played onto the foundations, and lost when no further play is possible.