Baker's Dozen is a solitaire card game using a deck of fifty-two playing cards. The game is so called because of the 13 columns in the game, the number in a baker's dozen.

First, the cards are dealt into columns of four on the tableau, resulting in 13 columns. Any King that is in the top or middle of each column must be placed on the bottom before the game starts. Two Kings that are mixed into one column are placed on the bottom without changing their order.

The object of the game is to build all the cards onto the four foundations. The player must first free up the four aces and if one of them is found, it is placed on the foundation. Building on the foundation is up by suit, each from ace to king.

Only the top cards of each column can are available, and cards on the tableau, if they cannot be placed on the foundations yet, can be built down regardless of suit. Furthermore, once all cards are taken out of a column, the column can never be filled.

The game is won when all cards end up in the foundations.

Here are some variations of Baker's Dozen:

• In Good Measure, two aces are taken out and placed on the foundations while the rest of the deck is shuffled and laid out in columns of five cards, resulting in 10 columns. Like in Baker's Dozen, Kings that are at the top or in the middle of their respective columns are placed at the bottom and the game proceeds in the process stated above.
• In Spanish Patience, Kings are left alone after dealing and empty columns can be filled by any card during game play.
• Castles in Spain is akin to Spanish Patience, but the cards in the tableau are built down by alternate color.
• Portuguese Solitaire is halfway between Baker's Dozen and Spanish Patience because empty columns can only be filled with Kings.