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Sudoku Strategy and Tips

Here is how to think about winning at Sudoku, split into short lessons. Each one reads on its own, and each one comes with a real position: press Try it on the board and you play the move yourself.

The one number missing from a row

Lesson 1

The quickest way to solve fast is to start where there are fewest empty squares. If a row, column or box has only one empty square, the only number that fits is the one missing. It needs no thought, so in a race you scan the whole grid first and clear these spots.

Each number you place also shrinks the empty squares in its column and box, often creating another one-gap spot. In a race where everyone has the same puzzle, how quickly you spot these chains makes the difference.

Here the third row already has 1, 5, 4, 2 and 6, and only its right-hand square is empty. The missing number is 3, so put 3 there.

Combine row, column and box

Lesson 2

Where there are two or more empty squares, focus on one square and strike out the numbers that can't go there: anything already in its row, column or box. Combining all three often leaves just one number.

In a race, start with squares where nearly full rows and columns cross; the more you strike out, the sooner you reach a single candidate.

Here, look at row 5, column 3. Its column has 1, 3, 4 and 6, its row has 4 and 3, and its box has 2. Only 5 is left, so put 5 there.

Check columns the same way

Lesson 3

One-gap spots show up not only in rows but also in columns and boxes. In a race, decide an order — rows, then columns, then boxes — and sweep the grid that way. Having a fixed direction for your eyes means almost no time is lost deciding where to look.

When the top rows are nearly full, a column often has a single gap near the bottom. If you only scan rows you can miss it, so trace downward on purpose too. Each number you place shrinks the gaps in its row and box as well.

Here the left column already has 2, 5, 1, 3 and 4 from the top, and only the bottom square is empty. The missing number is 6, so put 6 in the bottom-left square.

Pencil in candidates when unsure

Lesson 4

The biggest time sink in a race is getting stuck on one square. If a square isn't certain, pencil in its possible numbers with [Notes] and fill the certain spots first. As its neighbours fill up, the candidates naturally shrink to one.

Only note the numbers that remain after striking out those already in the row, column and box — writing every number takes longer to read. Notes on squares with two or three candidates make your next target easy to spot when you sweep the grid.

Here the top-left square has a 6 in its row and a 1 and a 4 in its column, so it must be 2, 3 or 5. Turn on [Notes] and pencil in the candidate 2.

Try it on the board

Pick a lesson and the board starts from that position. Start over as often as you like.

Now put it to work

Play with friendsLearn how to play (3 min)

Last updated 2026-10-05 · Run by Qdan, Inc.