Medium Sandwich Sudoku

Clues outside the grid give the sum of digits sandwiched between the 1 and the 9 in each row and column.

Easy Medium Hard Expert

Sandwich Sudoku at medium difficulty. Pinning down the positions of 1 and 9 in each row and column is the core technique.

0
6
15
15
11
33
0
4
0
25
0
23
0
18
35
27
15
3
1
6
7
1
5
5
6
9
2
4
8
2
1
6
7
5
7
8
4
1
7
4
5
8
5
6
4
2
4
1
7
8
Mistakes
0/3
Score
-
Time
00:00
Try Hard Sandwich Sudoku →
Progress0%

What is Sandwich Sudoku?

Difficulty
★★★★☆
4/5
Constraint Type
Outside Clues
Typical Givens
4–10 clue values
Avg. Solve (Medium)
26 min

Solving Techniques for Medium Level

Technique Description 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
Digit Forcing from Both Sides Use clues from both the row and column sides to triangulate the positions of 1 and 9 simultaneously. Intermediate

Master these, then take on Hard Sandwich Sudoku to learn Advanced techniques.

Techniques to Master at Medium

  • Hidden Singles technique — After fixing a row's 1 and 9, the filling must hit the clue sum exactly — digits too large for the remaining sum are evicted, and their hidden singles appear outside the sandwich.
  • Obvious Pairs technique — A two-cell filling summing to a clue like 5 is only {2,3} — sandwich arithmetic mass-produces obvious pairs that then eliminate across rows and boxes.

Average Solve Time by Difficulty

Easy
12 min
Medium
26 min
Hard
52 min
Expert
85 min
Want a full walkthrough of rules, strategies, and solving steps? How to Play Sandwich Sudoku →

Related Variants

Killer Sudoku

Both are sum-deduction puzzles at heart — killer's 45 rule and sandwich's crust sums exercise the same arithmetic.

Skyscraper Sudoku

Outside clues again, but read as building visibility instead of sums — the same edge-of-grid deduction style.

Outside Sudoku

The gentlest outside-clue cousin: border digits simply belong in the nearest three cells, no arithmetic required.

Frequently Asked Questions — Medium Sandwich Sudoku

What is the key technique for medium Sandwich Sudoku?
Position analysis for 1 and 9: for each row and column, list the valid positions for 1 and 9 that produce the given sandwich sum. Use standard Sudoku constraints (box uniqueness, naked pairs) to eliminate invalid positions, then determine the sum of the remaining middle digits.
How does knowing the sandwich sum help place digits other than 1 and 9?
Once you know the range of cells that are sandwiched, the sandwich sum constrains which digit combinations fill those cells. For a 3-cell sandwich summing to 12, the possible sets are {3,4,5}, {1,2,9}... but 1 and 9 cannot appear inside the sandwich, so only {3,4,5} works. This limits the middle cells' candidates immediately.
What happens when the 1 and 9 swap positions between two valid arrangements?
If two valid arrangements place the 1 on the left or the 9 on the left, the sandwich cells change length. In both cases, however, certain positions must belong to the sandwich and others never do. Cells outside all valid sandwich ranges for a given sum can be confirmed as holding non-sandwich digits.
How long does medium Sandwich Sudoku take?
Most players finish medium Sandwich Sudoku in 15–30 minutes. Medium puzzles are designed so that a handful of 0- or small-sum clues provide quick footholds, after which standard Sudoku techniques handle the rest.
Can I solve Sandwich Sudoku without placing the 1 and 9 first?
You can make some progress, but placing 1 and 9 is almost always the most efficient starting strategy. Once 1 and 9 are positioned in several rows and columns, the sandwich cells are defined and their digit constraints become concrete rather than probabilistic.

More questions? See the full Sandwich Sudoku guide.