5×5, 6×6 and 12×12 Sudoku

The same rule at three more sizes: every row, column and box holds each value once.

In short

A 6×6 grid has 2×3 boxes and the values 1 to 6. A 12×12 grid has 3×4 boxes and the values 1 to 12. A 5×5 grid has no boxes; it is cut into five irregular regions instead. Small grids are quick games, a 12×12 is a long one, and the techniques you know from 9×9 work on all three.

The rules

6×6: every row, every column and every box holds 1 to 6 once. The boxes are two rows deep and three columns wide.

12×12: every row, every column and every box holds 1 to 12 once. The boxes are three rows deep and four columns wide.

5×5: every row, every column and every region holds 1 to 5 once. Five cells cannot make a box that tiles the grid, so it is cut into five regions of five cells, like Jigsaw. The 3,000 puzzles here use 1,767 different layouts.

6×6
12×12
5×5
Three puzzles from this site. The 5×5 grid is cut into tinted regions instead of boxes.

What the size changes

A cell on a 6×6 grid sees 12 others, on a 9×9 grid 20, and on a 12×12 grid 28. Fewer cells in view means more candidates in each cell, so on a 12×12 grid pencil marks matter more.

The boxes on 6×6 and 12×12 are not square. A 6×6 box meets two rows and three columns, so a digit locked in a box’s row is locked through three cells, but in its column through only two.

Small grids skip a step. On 6×6 almost every Hard puzzle (494 of 500) needs an XY-Wing or an X-Wing, because pairs rarely decide anything in a house of six.

Writing 10, 11 and 12

On 12×12 the values 10, 11 and 12 are shown as numbers. They are drawn a little smaller so they fit the cell, and in pencil marks each sits on a faint pill, so a 12 never reads as a 1 and a 2.

Prefer letters? Board Settings has a switch under Puzzle Styles that shows them as A, B and C. Either way, the keys A, B and C (or 0, - and =) enter 10, 11 and 12.

Worked examples

One position from each size, from real puzzles on this site, walked through by the same Next Step teacher you get in a game. Each one first says what its size changes, then the move.

A hidden single in a 2×3 box

Medium puzzle · Hidden Single

A 6×6 box is two rows deep and three columns wide: six cells that hold 1 to 6 once each.

Step 1 of 5Step 2 of 5Step 3 of 5Step 4 of 5Step 5 of 5

A region locks a digit into a line

Medium puzzle · Locked Candidates

A 5×5 grid has no boxes. The lit shape is a region: five cells that hold 1 to 5 once each, like a box.

Step 1 of 5Step 2 of 5Step 3 of 5Step 4 of 5Step 5 of 5

A naked pair in a 3×4 box

Hard puzzle · Naked Pair

A 12×12 box is three rows deep and four columns wide: twelve cells that hold 1 to 12 once each.

Step 1 of 6Step 2 of 6Step 3 of 6Step 4 of 6Step 5 of 6Step 6 of 6

The levels

The levels use the same technique scale as Classic, so a Medium puzzle needs the same techniques at every size. Every puzzle has one solution and can be solved by logic alone.

Easy5×5: 11–16 · 6×6: 16–22 · 12×12: 60–88 cluesNaked singles only.
Medium5×5: 8–13 · 6×6: 12–18 · 12×12: 48–74 cluesHidden singles and locked candidates.
Hard5×5: 7–12 · 6×6: 10–16 · 12×12: 46–66 cluesPairs, triples and quads. On 5×5 and 6×6, Hard also takes in the wings and fish.
Extreme12×12 only: 48–60 cluesX-Wing, XY-Wing and Swordfish.

Classic techniques, at any size

Every Classic technique works the same way; only the number of cells in a house changes. These lessons teach them:

Naked SingleA cell with one candidate left. On 6×6 there are only six to rule out.Hidden SingleA house with one place left for a value, in a row, column, box or region.Locked CandidatesNon-square boxes lock through three cells one way and two or four the other.Naked PairCommon on 12×12, where a box of twelve leaves room for pairs.Hidden PairTwo values confined to two cells of a house.X-WingA row and column pattern, as in Classic. Frequent in Hard 6×6.XY-WingNeeded by almost every Hard 6×6 puzzle.SwordfishThree rows and three columns; it appears on 12×12 Extreme.

Frequently Asked Questions

Why does 5×5 have regions instead of boxes?

A box has to be a rectangle that tiles the grid, and five cells only make a 1×5 strip, which would just repeat a row. So the grid is cut into five irregular regions of five cells, as in Jigsaw.

Why is there no Extreme on 5×5 and 6×6?

The grids are too small for it. Puzzles there go from singles straight to wings and fish, so Hard covers everything past Medium.

Can I show 10, 11 and 12 as letters?

Yes. Board Settings, Puzzle Styles, then 12×12 values: choose A B C. The puzzle is the same; only the display changes.

How do I enter 10, 11 and 12?

Tap them on the number pad, or use the keys A, B and C (or 0, - and =).

Which tools can I use?

All of them: pencil marks in corner or centre notation, candidates, Auto Check, Check Cell and Check Puzzle, and Next Step.

How long does a 12×12 take?

Longer than a 9×9: it has 144 cells against 81. A 6×6 is the quick one, with 36.

Try one now. Easy is a good place to start.

The worked examples, every step

A hidden single in a 2×3 box

Medium puzzle · Hidden Single

  1. A 6×6 box is two rows deep and three columns wide: six cells that hold 1 to 6 once each.
  2. Look at box 1. The digit 4 must go somewhere in this box. Where can it go?
  3. R1C3 is the only cell in box 1 that can still take 4. Every other cell is filled or already sees a 4. Each arrow runs from a 4 to a cell it rules out.
  4. Place 4 in R1C3.
  5. R1C3 is now 4.

A region locks a digit into a line

Medium puzzle · Locked Candidates

  1. A 5×5 grid has no boxes. The lit shape is a region: five cells that hold 1 to 5 once each, like a box.
  2. In region 3, find every cell that can still take 3.
  3. All of them (R2C1, R3C1) are also in column 1. Region 3 must have a 3 somewhere in those cells, so the rest of column 1 cannot. The arrows point to the cells that lose 3.
  4. Eliminate 3 from R1C1.
  5. Done: 3 is eliminated from R1C1.

A naked pair in a 3×4 box

Hard puzzle · Naked Pair

  1. A 12×12 box is three rows deep and four columns wide: twelve cells that hold 1 to 12 once each.
  2. 12 is one value here, the same as 7. In the pencil marks it sits on its own faint pill, so it never reads as a 1 and a 2. The lit cells are the ones in this box that can still be 12.
  3. In box 7, look for two cells that hold the same two candidates between them.
  4. R7C1, R7C4 hold only {7, 12}. Those two digits must fill those two cells, so no other cell in row 7 and box 7 can use them. The arrows point to the cells that lose them.
  5. Eliminate {7, 12} from R7C2.
  6. Done: 7 is eliminated from R7C2.

Keep Going

See the Learning Hub for every Classic and Killer technique, or the glossary for the full vocabulary. New to Sudoku? Start with how to play.