Sandwich Sudoku: rules, strategy and how to start
A sandwich clue is the total of everything between the 1 and the 9 in a row. It sounds like arithmetic; in practice it is a placement puzzle for two digits.
Why the rule changes everything
The first deduction is always the same: find where 1 and 9 can sit. A clue of 0 means they are adjacent; 35 means every other digit lies between them and they must occupy the two ends.
Once 1 and 9 are placed, the clue tells you whether the remaining digits fill a wide or narrow window, which immediately constrains the outer cells of that row.
How to start a board
- Handle the extremes first: 0 forces adjacency, 35 forces the ends.
- For each clue, list the possible positions of the pair (1, 9) and eliminate using the 1s and 9s already visible in the grid.
- Only after placing the pair should you think about the sum itself.
Common mistakes
- Counting the 1 and the 9 in the sum.
- Assuming the 1 is on the left and the 9 on the right — order is free.
- Forgetting the maximum: a clue of 35 means every other digit is inside, so both ends are the pair.
Frequently asked questions
What is the largest sandwich clue?
35, the sum of 2+3+4+5+6+7+8.
What does a 0 mean?
The 1 and 9 touch, in either order, with nothing between them.
Every board on this site is generated with a uniqueness check, so the puzzle in front of you has exactly one solution and every digit can be proved rather than guessed.
Play Sandwich Sudoku ↗