Sudoku Tips and Strategies

Hi! My name is Steve, and I am a Sudoku enthusiast. My wife would likely use a different adjective.

I have studied how to solve a typical 9x9 Sudoku puzzle at some length, and have developed a modest but powerful repertoire of potential tips for human solving of a Sudoku puzzle using logic.

The goal of these pages is not only to provide those tips to others, but also to learn new ways of looking at the puzzles.

Hopefully, these pages will invite a free discussion and exchange of ideas regarding manners and methods to humanly solve sudoku puzzles.

Please check out the conventions that I use to label the puzzle grid, and other aspects of language used - including the rules of Sudoku as I see them. This will aid greatly in uniformity of discussion here.

Some Sudoku Definitions

The integers 1 through 9
Small containers that in a solved Sudoku will contain exactly one candidate each. This is one of the normally unwritten rules
Boxes, Rows, Columns
Large containers of cells.
The rule
In a solved sudoku, each large container will contain exactly one of each candidate.
The additional rule
Each Sudoku puzzle has a unique solution.

If the number of cells in each large container equals the number of potential candidates, (as is the case with typical 9x9 Sudoku), the following statements are equivalent:

  • There must be at least one of each candidate in each large container
  • There can be no more than one of each candidate in each large container
Most techniques employ both of these ideas.

Sudoku Puzzle Coordinates

This is completely arbitrary, but I prefer the algebraic notation like that used with chess. Thus the bottom left corner cell is a1, and the top right corner cell is i9. Unfortunately, there is very little uniformity regarding Sudoku puzzle coordinate choices across the web. One can argue that one is better than the other, but they are all completely arbitrary. Additionally, the boxes are defined by the label of their center cell. Thus, the bottom left corner box is Boxb2, or Bb2.

puzzle grid

I have created lots of posts on different solving techniques. Here are some to get you started:

Indicate which comments you would like to be able to see

Welcome to my sudoku blog!
Some of you may already be familiar with my propensity to post a bit too much....
A few things about me:
I live in Cincinnati, Ohio where I operate and own a small masonry construction business. I am blissfully married to perhaps the only woman on earth who More...
terrific idea-long overdue.Look forward to learning more.
Thanks to Gath for this site and to you Steve for taking it on. I have read your solutions a few times but at times find them somewhat confusing so I look forward to all being revealed. I struggle to solve the tough on most days if I do manage to solve it most of the comments from regulars are that it was too easy.
I have been playing with sudoku puzzles for a little while and love them. But have found that the tougher puzzles take me a long time. I can't wait for your tips and advice. When will you begin your blog? I do not know how to access a blog, so if you can include that information, I would be grateful. Thank you for your generosity.
Hullo Steve. A marvellous idea! I've been reading your proofs for a fair while and have learnt quite a bit from them. Altho I've been studying Sudoku techniques on the web, there are still a lot of questions - like how rectangular does an XY wing have to be? (Sometimes mine seem to tend towards the More...
Hi Steve. I haven't had time to do toughs in quite a few months, but I remember your proofs as being very helpful. I hope I'll get a chance soon to check all this out.
Hi Linda from Ohio!
(A great state, BTW). This is the blog, right here. Additional pages will be added periodically. The blog pages will introduce progressively more complicated tips and techniques - and also some hints on how use that information.
Thanks, Steve. Buckeyes rule. I look forward to learning much here.
Wow!! This is great!! Oftentimes I thank you Steve, when the 'hints' say it is tooooo tough, and I look down at the comments and find that something-or-the-other forbids a cell being a certain number 'up to 81', and IF I have done the setup correctly, it all comes out right!!! Now perhaps I can learn why!!
hopefully i will learn the language of proofs here. thank you.
Thanks Gath and Steve. I look forward to the help. I have been stuggling with a book of 'extremely tough' puzzles. Some have taken a day to complete.
Thanks Gath & Steve. This is a great idea - I generally am rather sporadic at getting to the tough puzzles on this site and often don't understand Steve's proofs so I am really looking forward to learnng some new and better technigues for the harder puzzles. Most of the time I am working sudokus More...
Hello Steve - Thanks for taking the time to do this.

Gath - As always, you are great. Thank you
Great idea, I'm in! You can count on me to be a regular visitor.
Steve and Gath, this is wonderful! All of us regular toughies really appreciate it. And Steve, it was fun to read about what you do when you aren't doing sudoku. It's such an amazing thing to have this international community where we all get to know each other. Thanks again!
Thanks Steve for providing another brick in the Sudoko wall! Your proofs have been a tremendous tool in learning the logic behind the solutions.
Thanks Steve, I need this help. I am slow and often get blocked on hard. Intuition and revelation are poor substitutes for logic.
have been looking forward to this for a long time!
thanks Steve & Gath
Hi Steve. I'm a bit of a 'look and try forever' person on the toughs. Have tried to figure out your solutions in the past but got a little lost at times. Thanks for this page. Very helpful!
This promises to be very good - but is the information going to be daily, weekly, random...?
The 'plan', subject to change without notice, is to publish two new blog pages per week.
Hi Gil (from gippsland)!
Eventually, more complex techniques like xy wings will be discussed at some length.
Quite a while back, on the tough puzzles page, I may have railed a bit against the guardian technique. In the face of an idea that is new to me, I am always a skeptic. Perhaps I did More...
Great stuff - your explanations are spot on.
I like your use of algebraic notation, and use of defined vocab like 'container' and 'candidates'. You and your readers may find the freeware Sudoku generator/solver at of interest.
Hi Steye. Your information on the net was extremely useful. I shall be highly obliged if you enlighten me more on BUG from fundamentals. Thanks

06/Aug/07 12:31 AM
If you want to try out something new in sudoku, try shendoku, using the sudoku rules but playing two people, one against the other, like battleshipps. They have a free version to download at . Anything else they are bringing out or they are working on you can find More...
08/Oct/07 8:23 AM
Check out Sudoku Learning Center(SudokuLearningCenterdotCom)

It has a great set of online tutorials on the various techniques to solve Sudoku puzzles along with specially designed puzzles to aid in mastering the various techniques.
03/Nov/07 10:33 AM
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