Sandwich Sudoku
0
0
9
13
15
0
0
0
0
0
35
35
8
8
0
18
6
19
8
1
3
4
7
4
6
8
1
1
2
3
4
7
5
8
9
6
9
1
7
7
4
4
7
3
6
3
4
2
7
5
9
8
9
4
1
3
How to play Sandwich Sudoku
Standard Sudoku rules apply. The blue numbers on the left indicate the sum of digits sandwiched between 1 and 9 in that row. The blue numbers on top indicate the same for each column.
Full guide →
Clues give the sum of digits between the 1 and 9 in each row/column
Easy
Sandwich Sudoku Easy
Medium
Sandwich Sudoku Medium
Hard
Sandwich Sudoku Hard
Expert
Sandwich Sudoku Expert
What is Sandwich Sudoku?
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
| Constraint type | Outside Clues |
| Typical givens | 4–10 clue values |
| Difficulty rating | ★★★★☆ 4/5 |
| Avg. solve time — Easy | 12 min |
| Avg. solve time — Medium | 26 min |
| Avg. solve time — Hard | 52 min |
| Avg. solve time — Expert | 85 min |
How to Solve Sandwich Sudoku
| Technique | What it does | Level |
|---|---|---|
| Clue 0 Means Adjacent 1 and 9 | A sandwich clue of 0 means 1 and 9 are side-by-side with nothing between them. Place this pair immediately. | Beginner |
| Clue 35 Means 1 and 9 at Ends | A clue of 35 = 2+3+4+5+6+7+8. All middle digits are sandwiched, placing 1 and 9 at the two ends of the row/column. | Beginner |
| Position Enumeration | For each clue, enumerate all valid positions of 1 and 9 such that the enclosed digits sum to the clue. Cross-reference with column clues. | Intermediate |
| Sandwich Intersection | Row and column clues intersect at one cell. Combining row positions of 1 and 9 with column positions pinpoints key placements. | Advanced |
| Digit Forcing from Both Sides | Use clues from both the row and column sides to triangulate the positions of 1 and 9 simultaneously. | Intermediate |
Average Solve Times
Easy
12 min
Medium
26 min
Hard
52 min
Expert
85 min
Frequently Asked 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.