A LITTLE FOCUS. A FRESH START.
Play Sandwich Sudoku
Play Sandwich Sudoku free online. Outside clues reveal sums between 1 and 9, adding a new layer of logic to the classic 9×9 grid.
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LEARN THE TWIST
How to play Sandwich Sudoku
Clues sit outside the grid and apply only to digits strictly between 1 and 9 in that row or column. An unmarked row or column has no extra sandwich restriction.
The rules
Fill each row, column, and 3×3 box with 1–9, without repeats. Outside clues give the sum strictly between 1 and 9 in a row or column. Zero means they are adjacent. Unmarked rows and columns have no extra restriction.
A useful first move
Locate the two “bread” digits, 1 and 9, then work out which intervening digits can make the clue. Their order can be reversed: either 1 or 9 may come first.
In a row segment reading 1, 2, 5, 9, the sandwich total is 7. The 1 and 9 are not included. A clue of 0 means the 1 and 9 must be adjacent.
SOLVE IT STEP BY STEP
Find the filling, then subtract what you know
A Sandwich clue counts only the digits strictly between 1 and 9 in its row or column. Those two digits act as the ends. Locating them turns a long row into a smaller sum problem, and the rest of the row does not contribute to that clue.
- Unknown filling cell
- 5
Locate both ends.
The 1 is in column 2 and the 9 is in column 5. Only columns 3 and 4 lie strictly between them.
Write the filling sum.
The filling must total 7, so 2 + empty = 7. Neither the 1 nor the 9 is included, and neither are the cells before or after them.
Complete the filling.
The empty filling cell is 5. The row still needs ordinary Sudoku solving outside the sandwich; the clue does not specify those other cells.
Use extreme clues to locate the ends
A clue of 0 means no cells lie between 1 and 9, so they must be adjacent. At the other extreme, 35 is the sum of all digits 2–8. A clue of 35 therefore puts 1 and 9 at opposite ends of the row or column. For intermediate clues, consider both the number of filling cells and the different digits that can make the total.
Common mistakes to avoid
- The order of 1 and 9 can be reversed without changing the filling sum.
- An absent outside clue imposes no Sandwich restriction; it does not mean a sum of zero.
Try the reasoning yourself
A row segment reads 9, 3, 6, 1. What Sandwich clue does it produce?
Show the answer and why
The clue is 9, because only 3 + 6 is between the endpoints. Reading 1, 6, 3, 9 produces the same clue.
Controls, difficulty, and saved games
Choose Beginner, Easy, Medium, Hard, or Expert above. Select an empty cell, then tap a number or use your keyboard. Notes let you pencil in candidates; three hints are available. Three mistakes end the puzzle.
Every mode and difficulty keeps a separate save in this browser. You can switch puzzles and return to your place. Clearing site data removes these saves; they do not sync with another device or the iPhone app. Settings include night mode and optional automatic cell advancement.
Correct entries earn points. High scores are stored by mode and difficulty and update only when beaten; completed-puzzle count and day streak are shared.
FIFTEEN WAYS TO PLAY
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A familiar grid, a different kind of logic. Every mode is free to play in your browser.