Mirrored from **Sudopedia**, the Free Sudoku Reference Guide

The **cell** is the smallest element of a Sudoku grid. It can contain only a single digit.

## Contents |

There are several cell naming conventions. Most of them use the row and column for identification. The most widely used format is **rncn**, where the cells are named according to the following lay-out:

.--------------.--------------.--------------. |r1c1 r1c2 r1c3|r1c4 r1c5 r1c6|r1c7 r1c8 r1c9| | | | | |r2c1 r2c2 r2c3|r2c4 r2c5 r2c6|r2c7 r2c8 r2c9| | | | | |r3c1 r3c2 r3c3|r3c4 r3c5 r3c6|r3c7 r3c8 r3c9| :--------------+--------------+--------------: |r4c1 r4c2 r4c3|r4c4 r4c5 r4c6|r4c7 r4c8 r4c9| | | | | |r5c1 r5c2 r5c3|r5c4 r5c5 r5c6|r5c7 r5c8 r5c9| | | | | |r6c1 r6c2 r6c3|r6c4 r6c5 r6c6|r6c7 r6c8 r6c9| :--------------+--------------+--------------: |r7c1 r7c2 r7c3|r7c4 r7c5 r7c6|r7c7 r7c8 r7c9| | | | | |r8c1 r8c2 r8c3|r8c4 r8c5 r8c6|r8c7 r8c8 r8c9| | | | | |r9c1 r9c2 r9c3|r9c4 r9c5 r9c6|r9c7 r9c8 r9c9| '--------------'--------------'--------------'

Alternatively, the rows are identified by letters. Some people skip the letter **I** to avoid confusing it with number 1, some also skip letter **J**. The last cell can therefore be either **I9**, **J9** or **K9**. This is also known as the **K9** format.

Here is the lay-out where the letter **J** is used for the last row:

.----------.----------.----------. | A1 A2 A3 | A4 A5 A6 | A7 A8 A9 | | B1 B2 B3 | B4 B5 B6 | B7 B8 B9 | | C1 C2 C3 | C4 C5 C6 | C7 C8 C9 | :----------+----------+----------: | D1 D2 D3 | D4 D5 D6 | D7 D8 D9 | | E1 E2 E3 | E4 E5 E6 | E7 E8 E9 | | F1 F2 F3 | F4 F5 F6 | F7 F8 F9 | :----------+----------+----------: | G1 G2 G3 | G4 G5 G6 | G7 G8 G9 | | H1 H2 H3 | H4 H5 H6 | H7 H8 H9 | | J1 J2 J3 | J4 J5 J6 | J7 J8 J9 | '----------'----------'----------'

In the larger Sudoku variants, two digits may be required to designate a row or column. In those cases, the lower numbers are often prefixed with a zero.

There are 81 cells in a standard Sudoku grid, but not in all Sudoku Variations. Here is a list with some alternative formats with the number of cells:

- 4x4
- 16 cells

- 6x6
- 36 cells

- 12x12
- 144 cells

- 16x16
- 256 cells

- 25x25
- 625 cells

- Samurai
- 369 cells

- Clueless
- 729 cells

- Hanidoku
- 61 cells

A cell can either be empty or contain a digit. An empty cell is also known as an **unsolved cell**.
Cells containing a digit are either given or **solved**.

There can be upto 9 candidates in a cell, one for each digit.

- Aliases
- square

- Contains
- between 2 and 9 candidates or 1 digit