The aim of Calculation is to build 4 piles, the foundation piles, according to their pattern, each completing with a King.

Calculation starts with 4 piles in the top row, the foundation, and 4 piles beneath them forming the tableau. The foundation piles start with Ace, 2, 3 and 4 respectively which are dealt at the start. The tableau piles are empty to start with. The remaining cards form the stock and are placed face-up ready for play.

As you pick up each card in the stock, you can place it either on a foundation or in the tableau piles. Each foundation runs in a different pattern. These are:
- First Foundation pile: built up in ascending rank, i.e. Ace 2 3 4 5 6 7 8 9 10 Jack Queen King
- Second Foundation pile: built up in twos, i.e. 2 4 6 8 10 Queen Ace 3 5 7 9 Jack King
- Third Foundation pile: built up in threes, i.e. 3 6 9 Queen 2 5 8 Jack Ace 4 7 10 King
- Fourth foundation pile: built up in fours, i.e. 4 8 Queen 3 7 Jack 2 6 10 Ace 5 9 King

Suit doesn't matter: any card can be played on any foundation, provided it follows the correct sequence. You can play any card on any of the tableau piles. Once in a tableau pile, a card can only be moved to a foundation unless you have changed the rules to allow tableau building.

Calculation is won when you have moved all the cards to the foundations. If you run out of moves before winning, the game is over.