Sudoku Notation (rNcN and Box Numbering)
How to name a cell with rNcN coordinates and refer to rows, columns and boxes — the shared language for discussing puzzles.
To talk about a Sudoku — in a guide, a forum, or your own notes — you need a way to name a specific cell. The standard is rNcN notation: r for the row, c for the column, each followed by its number. The cell in the third row and fifth column is r3c5.
Alongside cell coordinates, rows, columns and boxes are numbered 1–9 so they can be referenced directly. This article covers both, so the notation used across the rest of the wiki reads clearly.
rNcN cell coordinates
Rows are numbered 1 to 9 from top to bottom; columns 1 to 9 from left to right. A cell is written as its row then its column: r1c1 is the top-left cell, r9c9 the bottom-right. Ranges are common too — r2c3-5 means the cells in row 2, columns 3 through 5.
- r = row (1–9, top to bottom).
- c = column (1–9, left to right).
- r4c7 = the cell in row 4, column 7.
Numbering rows, columns and boxes
Rows are R1–R9 top to bottom and columns C1–C9 left to right. Boxes are numbered 1–9 reading left to right, top to bottom: box 1 is the top-left 3×3 block, box 5 the centre, box 9 the bottom-right. With this you can write a deduction unambiguously, e.g. "5 is a hidden single in box 5 at r5c5".
- Rows R1–R9, top to bottom.
- Columns C1–C9, left to right.
- Boxes 1–9, left to right then top to bottom (box 5 is the centre).
Frequently asked questions
- What does r3c5 mean?
- The cell in row 3, column 5. Rows are numbered 1–9 top to bottom and columns 1–9 left to right, so rNcN names any cell unambiguously.
- How are the boxes numbered?
- Boxes are numbered 1–9 reading left to right, then top to bottom. Box 1 is the top-left 3×3 block, box 5 is the centre, and box 9 is the bottom-right.
Related reading
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