Play Sandwich Sudoku Online

In Sandwich Sudoku, the 1 and the 9 are the bread. Add every digit between them along a row, then compare that total with the number printed beside the row. This board provides nine left-side sums, one per row. A zero clue means 1 and 9 sit next to each other.

1. Read the given digits; these dark numbers stay fixed.
2. Select an empty square and use the number buttons to enter a candidate from 1 to 9.
3. Put each digit exactly once in every row and column.
4. Put each digit once in every standard three by three box.
5. The clue to the left of each row equals the sum of all cells strictly between its 1 and its 9.
6. Use Clear to erase an editable cell. Complete the board and check the variant rules to win.
7. The nine numbers printed beside the board refer to rows, not columns. For each row, find the positions of 1 and 9 and add the digits strictly between them. Their order does not matter: 9, 2, 5, 1 has the same sandwich total as 1, 2, 5, 9. Outside digits do not count.
8. Start a row with a small clue by locating possible adjacent positions for 1 and 9. For larger clues, check whether the available digits between candidate endpoint positions can reach the printed sum. The number shown at the left is a sum, not a row index. Repeat this analysis after any new 1 or 9 appears elsewhere in the grid.

• Every row contains the digits 1 through 9 once.
• Every column contains the digits 1 through 9 once.
• Every standard three by three box contains 1 through 9 once.
• The clue to the left of each row equals the sum of all cells strictly between its 1 and its 9.
• A clue of zero makes the two endpoints adjacent, but it does not specify which one comes first or where they sit. A clue of 2 means exactly one digit, 2, can lie between them. Larger clues allow several arrangements, so use normal Sudoku exclusions to decide both endpoint positions and interior digits.

• Start with rows that have several given digits and list their missing values.
• A zero clue forces neighboring 1 and 9. A small positive clue limits how many cells can lie between them.
• Check columns crossing a marked constraint before placing a digit.
• When a region has just one empty cell, fill its missing value and revisit the variant clue.
• A complete standard Sudoku grid can still fail a variant rule. Review every marked constraint before the final move.

• Sudoku: Practice the standard number-placement rules before trying a variant.
• Arrow Sudoku: Compare how a related puzzle uses regions, paths or tile placement.
• Thermo Sudoku: Compare how a related puzzle uses regions, paths or tile placement.

• Each extra constraint adds a second way to narrow candidates.
• The number pad works with touch, mouse and keyboard focus.
• The variant rules reward scanning more than one region at a time.
• Sandwich clues turn row order into information. You can work from a given 1 or 9, or work backward from a small printed sum. The left-side sums recalculate for each new puzzle, so the clues always belong to the digits currently displayed. Check the row total after filling its final cell.

Play Sandwich Sudoku free in your browser. Start the interactive board above, use its on-screen controls and check the rules below when a deduction gets stuck. No download or account is needed.

Try another round of Sandwich Sudoku on the board above. Start with the most constrained part of the grid, test each move against the stated rules, and use the reset control to try a new approach.

• Variant Sudoku reference