Why 6×6 Sudoku boxes are 2×3 (not square)
6×6 Sudoku boxes are 2×3 because each box must hold the six digits 1–6 exactly once, so it needs six cells. Six isn’t a square number, so a square box can’t work; a 2-by-3 rectangle holds six cells and six of them tile the grid exactly.
The digits, the rows, and the columns are the rest of the rules. Those live on the 6×6 Sudoku rules page. This page is only about the box shape.
The short math: each box must hold six digits
Every row, every column, and every box contains each of 1–6 once. A box is one of those groups, so it holds six cells. Six is not a perfect square: there is no whole number n with n × n = 6. A square box cannot tile a 6×6 grid and still hold six cells. The rectangles that do both jobs are 2×3 and 3×2. Two rows by three columns is six cells, and those rectangles meet the outer edges without a leftover strip.
Compare with 9×9
Classic 9×9 Sudoku can use square 3×3 boxes because 9 is 3×3. A 4×4 grid uses 2×2 boxes. A 6×6 grid has to use rectangles. Mini Sudoku vs classic 9×9 compares the formats; the table here is only the box arithmetic.
| Grid | Digits | Box shape |
|---|---|---|
| 4×4 | 1–4 | 2×2 squares |
| 6×6 | 1–6 | 2×3 rectangles |
| 9×9 | 1–9 | 3×3 squares |
How the six boxes tile the grid
A 6×6 Sudoku has six boxes, arranged three down and two across. Each box covers two rows and three columns: rows 1–2, 3–4, or 5–6, and columns 1–3 or 4–6. Three box-rows times two box-columns is six boxes, and every cell sits in exactly one of them.
The six boxes, labelled
| Row / column | C1 | C2 | C3 | C4 | C5 | C6 |
|---|---|---|---|---|---|---|
| R1 | A , box A | A , box A | A , box A | B , box B | B , box B | B , box B |
| R2 | A , box A | A , box A | A , box A | B , box B | B , box B | B , box B |
| R3 | C , box C | C , box C | C , box C | D , box D | D , box D | D , box D |
| R4 | C , box C | C , box C | C , box C | D , box D | D , box D | D , box D |
| R5 | E , box E | E , box E | E , box E | F , box F | F , box F | F , box F |
| R6 | E , box E | E , box E | E , box E | F , box F | F , box F | F , box F |
Trace the thick lines before you scan. Two cells share a box only when they sit inside the same letter. R1C3 and R2C1 are both in A. R2C3 and R2C4 are neighbors in the row, and they are in different boxes: A and B.
2×3 vs 3×2: same idea, rotated
Some 6×6 puzzles draw boxes three rows tall and two columns wide instead. The rule is the same: each box contains 1–6 once. Our guides and Sudoku Sama use boxes that are two rows tall and three columns wide. This page does not treat either drawing as the only one in use.
What rectangular boxes change when you solve
A 2×3 box meets each of its rows in three cells and each of its columns in only two. A digit already in the box rules out three cells of a row, and only two cells of a column. The constraint is the same; the count of cells you cross out is not. Hidden singles on a 6×6 is the scan itself. In the worked example, a box is one of the clues that rules a cell out.
Seeing it in Sudoku Sama
Sudoku Sama is a daily 6×6 with these 2×3 boxes. Each day asks for one key placement, where a number belongs in a given row, and there is no timer. Today’s puzzle is free. The app is in English for iPhone and iPad and requires iOS or iPadOS 26 or later. You play in the app, not in the browser on this site. The how-to guide is the tap flow.
Download Sudoku Sama on the App Store
Daily 6×6 · one key placement · no timer · today’s puzzle free
FAQ
Why aren’t 6×6 boxes square?
Each box must hold six digits, so it needs six cells. Six is not a square number, so a square region cannot do that job and still tile the grid. The rules page states the 2×3 shape; this page is the reason.
How many boxes are in a 6×6?
Six. They sit three down and two across.
Is 3×2 different from 2×3?
It is the same idea, rotated: three rows tall and two columns wide. Each box still contains 1–6 once. Sudoku Sama and these guides use two rows by three columns.
Do diagonals count?
No. Unless a puzzle explicitly adds a variant rule, diagonals do not need to contain 1–6.
Download Sudoku Sama on the App Store
Daily 6×6 · one key placement · no timer · today’s puzzle free
About Sudoku Sama · 6×6 rules · Mini vs classic · Hidden singles · Worked example