Sandwich Sudoku Puzzles

The below information tells you the rules of sandwich sudoku, and how to play it. You can also:

- play a sandwich sudoku online, and

- play a puzzle a day via our new puzzle site.

Of the many sudoku variants that exist, sandwich sudoku is one of the most intriguing. There are at least two different sudoku variants known by this name:

1) A puzzle where one-or-more numbers may be given outside the grid at the start or end of rows/columns. In this variant, the number 8 at the start of a row would mean that the 8 was sandwiched between other numbers that sum up to 8 (583, for instance, or 682 or 781 in some order).

2) A puzzle where numbers are given at the start or end of every row/column, and these numbers indicate the sum of the values between the 1 and 9 in that row or column (or 1 and 6, for a 6x6 sudoku)

In this article, we are focusing on the second of these sudoku variants known as sandwich sudoku, which you may also have come across under names such as between-1-and-9 sudoku or between-1-and-6-sudoku. These drier-sounding names indicate more clearly how the tasty puzzle works. Here are the instructions for those of you new to this novel sudoku variant:

The appeal of sandwich sudoku is that there are many different pieces of solving logic that it introduces, and some of these are quite subtle. The more puzzles you tackle, the more you realise how much 'sandwich logic' can be applied, and it is integral to the solve of the puzzle. This contrasts with some variants where the new logic either isn't particularly interesting, isn't actually used a great deal, or doesn't have much depth.

Familiarity with totals that can sum to given numbers, as with kakuro and killer sudoku, is very important to making progress with these puzzles. In a 9x9 sandwich Sudoku (or any other size), the smallest number that can appear outside the grid is 0, this means that the 1 and 9 are adjacent in the grid. If you know where one of them is, you know where the other is. If you have 1 as a candidate for the first square in a row whose sandwich value is 0, but the second square doesn't have 9 as a candidate, then you know the first square doesn't contain a 1.

The highest sandwich score for a 9x9 sandwich sudoku is 35. This is the sum of the numbers 2,3,4,5,6,7,8. Therefore if you see a 35 outside a row or column, then you can place 1/9 as the only candidates for the first and last squares in that region.

Knowing how big a sandwich can be is sometimes key to making progress with sandwich sudoku puzzles, not just in the extreme cases but lots of intermediate ones, too. When solving a sandwich sudoku, usually the first thing you need to do to make progress is to work out where the 1s and 9s can go in as many regions as possible. Therefore you'll need to consider cases where you know where one is in a region but not the other, and also cases where you don't know where either are. If a 1 and a 9 are placed already in a region, then you can consider what values can be placed between them to make the required sum, and often make further progress by doing so.

Play Sandwich Sudoku Puzzles

If you'd like to have a go at a sandwich Sudoku puzzle in print, then you can play the Sandwich Sudoku Puzzle shown above-right on this page. The solution is on the second page of the PDF, we hope you enjoy it.

If you want to play online, then here are two puzzles for you to play:

1) Play a 6x6 Sandwich Sudoku. The puzzle uses a 6x6 grid so you must work out the numbers sandwiched between 1 and 6 here.

2) Once you've solved that, use our Online Sandwich Sudoku Player to try a trickier 9x9 puzzle.

Enjoyed the samples? Then why not join our Puzzle Connoisseur's Club and have access to 365 sandwich Sudoku puzzles over the course of a year, along with many other fun Sudoku/number/logic puzzles.

Finally, if you like a whole book of sandwich Sudoku puzzles, we have a Sandwich Sudoku Book book available to buy now, containing 50 6x6 puzzles and 50 9x9 puzzles.

Remember to use the tips above to help you work out where the 1s and 9s can go in each region to help you get started. For instance, look at the 9 in column two. You can use the position of the 9 and 7 in the column, together with the sandwich total of 11, to place the digits immediately above and below the 7 straightaway. Can you see why, and what they are?

Do you like sandwich sudoku? Have you found any useful solving tips or tricks you'd like to share? Feel free to post your thoughts about sandwich sudoku below.
Date written: 18 May 2019

Category: sudoku | Keywords: Sudoku | sandwich

Comments:

I absolutely LOVE sandwich Sudoku, but can only find one a week published currently... where can I find more?
By: James - 30 Jul 2019 11:48:42

Hi James, great to hear that you enjoy sandwich Sudoku puzzles! We do have a book containing 50 6x6 puzzles and 50 9x9 puzzles available to buy, via this link: Sandwich Sudoku Puzzle Book
By: Clarity Media - 31 Jul 2019 13:28:38

Regular Sudoku has gotten too boring, completed in 5 minutes or less most of the time.Thank you for the increased challenge!!! I am now waiting on an app to be written.
By: Beth Lourias - 23 Aug 2019 07:31:27

Thanks for the positive feedback Beth, glad to hear you enjoy sandwich sudoku! You can now play a puzzle a day, along with several other logic puzzles a day, by joining our Puzzle Connoisseur's Club. We hope this will be of interest to you!
By: Clarity Media - 24 Aug 2019 19:21:46

I've seen this puzzle in the paper but not too sure how to get started, any chance you could add a walkthrough of a solve to that video?
By: Jeff Thomas - 17 Sep 2019 15:59:59

Hi Jeff, Thanks for the suggestion - we've now added a full walkthrough of the solve of the 6x6 sandwich Sudoku example which you can view on the Clarity Media Youtube Channel.
By: Clarity Media - 23 Sep 2019 13:21:05

Puzzle Videos: Learn to Solve

How to solve Jigsaw Sudoku
Been tempted by jigsaw sudoku but found it too tricky, or perhaps you've tried but got stuck? This video walks through the solve of a jigsaw (irregular) sudoku, and you can try the puzzle before you watch...

Would you like to have a go at solving the puzzle? You can do so here: Online Jigsaw Sudoku Puzzle

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