How to Play Sandwich Sudoku
Clues give the sum of digits between the 1 and 9 in each row/column
The Rules
Standard Sudoku rules apply: fill every row, column, and 3×3 box with the digits 1–9, each appearing exactly once.
Sandwich Sudoku places clues along the outside of the grid. Each clue gives the sum of all digits squeezed between the 1 and the 9 in that row or column. The positions of 1 and 9 vary, so the 'sandwich' can have 0 to 7 cells depending on where they land. A clue of 0 means 1 and 9 are adjacent. A clue of 35 means all digits 2–8 are between them.
At a Glance
How to Solve Sandwich Sudoku
Common Questions
What is Sandwich Sudoku? ▾
Sandwich Sudoku is a variant where clue numbers appear outside the grid, one per row and one per column. Each clue tells you the sum of all digits that appear between the 1 and the 9 in that row or column. Standard Sudoku rules apply throughout.
How do I use the sandwich clues? ▾
First, find the positions of the 1 and 9 in each row or column — every other digit between them must sum to the outside clue. A clue of 0 means the 1 and 9 are adjacent. A clue equal to the maximum possible sum (e.g., 35 for a 7-cell sandwich) tells you the 1 and 9 are at the ends. Work from the most constrained clues first.
What does a sandwich clue of 0 mean? ▾
A clue of 0 means no digits are sandwiched between the 1 and 9 — they must be directly adjacent to each other. This is one of the most powerful clues because it immediately tells you where 1 and 9 can and cannot be placed relative to each other in that row or column.
Is Sandwich Sudoku harder than regular Sudoku? ▾
Yes, generally. Sandwich Sudoku provides very few pre-filled digits inside the grid. Almost all deductions flow from working out where 1 and 9 can sit and what sums are achievable. The logic is more algebraic than classic Sudoku, which many players find both more challenging and more satisfying.
Can the 1 and 9 be at the ends of a row? ▾
Yes. If the 1 is in column 1 and the 9 is in column 9 (or vice versa), the sandwiched digits are columns 2–8, giving a maximum possible sum of 2+3+4+5+6+7+8 = 35. Extreme clue values like this immediately fix the positions of both the 1 and the 9.
How long does Sandwich Sudoku take to solve? ▾
Easy puzzles typically take 10–20 minutes. Medium puzzles run 20–35 minutes. Hard puzzles can take 45–75 minutes, and expert puzzles often exceed 90 minutes. The key bottleneck is working out 1/9 positions — once you pin those down, the rest of the grid often resolves quickly.