The 27 Houses of Sudoku

/ Beginner Tutorials

Understanding what a house is in a Sudoku puzzle is a key element to understanding puzzle solving techniques. A “house” in Sudoku is a group of nine numbers of 1-9 where each number only occurs once. A house can be a row, column, or 3 x 3 block. There are 27 houses in a Sudoku puzzle. Each house with the puzzle below will be identified.

Consider this puzzle (the image above)

Here are the row houses numbered 1 through 9 from top to bottom highlighted with a black outline:

The house making up row 1 (the image above)
The house making up row 2 (the image above)
The house making up row 3 (the image above)
The house making up row 4 (the image above)
The house making up row 5 (the image above)
The house making up row 6 (the image above)
The house making up row 7 (the image above)
The house making up row 8 (the image above)
The house making up row 9 (the image above)

Here are the column houses numbered 1 through 9 from left to right highlighted with a black outline:

The house making up column 1 (the image above)
The house making up column 2 (the image above)
The house making up column 3 (the image above)
The house making up column 4 (the image above)
The house making up column 5 (the image above)
The house making up column 6 (the image above)
The house making up column 7 (the image above)
The house making up column 8 (the image above)
The house making up column 9 (the image above)

Here are the block houses numbered 1 through 9 from left to right and top to bottom highlighted with a black outline:

The house making up block 1 (the image above)
The house making up block 2 (the image above)
The house making up block 3 (the image above)
The house making up block 4 (the image above)
The house making up block 5 (the image above)
The house making up block 6 (the image above)
The house making up block 7 (the image above)
The house making up block 8 (the image above)
The house making up block 9 (the image above)

Some people use the word “box” instead of “block”. But we like the word block because prison blocks have cells and the word box is too ambiguous with the 81 cells, 9 blocks, and the puzzle perimeter.

These are 27 houses of Sudoku.