A house is any row, column, or box - a group of nine cells that must contain the digits 1 through 9 exactly once.
A house is the general term for any group of nine cells in Sudoku that must contain all digits from 1 through 9 without repetition. The standard 9x9 Sudoku puzzle has 27 houses in total: 9 rows, 9 columns, and 9 boxes. Every cell belongs to exactly three houses.
The term was adopted by the Sudoku community because many solving strategies apply identically to rows, columns, and boxes. Instead of saying "a naked pair in a row, column, or box," strategists can simply say "a naked pair in a house." This makes explanations more concise and easier to understand. For complete rules, see our Sudoku rules guide.
Each type of house provides a different spatial constraint on the puzzle. Rows run horizontally across the grid, columns run vertically, and boxes are the 3x3 sub-grids. While they differ in shape and orientation, the rule is the same for all: each must contain every digit exactly once.
9 horizontal lines of 9 cells each, running left to right across the grid. Numbered 1 (top) through 9 (bottom).
9 vertical lines of 9 cells each, running top to bottom. Numbered 1 (left) through 9 (right).
9 square sub-grids of 3x3 cells each, outlined by thicker borders. Arranged in a 3x3 pattern.
Almost every Sudoku strategy is defined in terms of houses. Hidden singles look for a candidate that appears in only one cell within a house. Naked pairs find two cells in the same house that share exactly two candidates. Pointing pairs exploit the intersection of a box with a row or column.
When reading strategy guides, the term "house" saves considerable repetition. Instead of explaining each technique three times - once for rows, once for columns, and once for boxes - guides explain it once using the word house, and you understand it applies to all three. Visit our strategies page to see these concepts in action.
Explore more terms in the Sudoku glossary.
A house is any group of nine cells that must contain all digits 1 through 9 exactly once. In standard Sudoku, there are 27 houses: 9 rows, 9 columns, and 9 boxes. The term is a convenient shorthand used in strategy discussions.
The term house was adopted by the Sudoku community as a convenient way to refer to any row, column, or box without specifying which one. Since many strategies apply equally to all three types, using the word house makes explanations more concise and general.
Every cell in a standard Sudoku puzzle belongs to exactly three houses: one row, one column, and one box. This means each cell is constrained by three separate groups, all of which must contain the digits 1 through 9 without repetition.
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