How to Solve Sudoku 9×9 Puzzles In 9 Simple Steps

Hello and welcome to this article all about Sudoku 9×9 Puzzles. If you have got here by mistake and are looking for Sudoku puzzles in general, click on this link, and check out all the puzzles I do.

The basic idea for ANY Sudoku puzzle is to complete the grid (no matter its size) by filling in the empty squares with numbers from 1 to whatever size the grid is. Therefore, if you are completing a Sudoku 9×9 puzzle, the numbers would be from 1 to 9; a Sudoku 12×12 puzzle, the numbers from 1 – 12; a Sudoku 16×16, from 1 – 16 and so on.

Of course, there are many other types of Sudoku puzzles, Sudoku Marathon, Sudoku Samurai, Sudoku Twins to name just a few. Generally, these puzzles are made up of Sudoku 9×9 puzzles with a twist. If you want to see a full range of Sudoku puzzles, head over to my Amazon Author’s Page. Anyhoo, back to Sudoku 9×9 puzzles.

Also, just to let you know, in the images I use, I am going to number the rows and columns from 1 – 9. This is purely to help me explain the steps. When you do real Sudoku puzzles, these numbers are not there because you don’t need them. We’re also going to use some images from now on to help me explain things. I’ll let you know which one I am referring to as we go along.

How to Solve Sudoku 9×9 Puzzles

Here is the puzzle we are going to be working on together. If you want, copy it on to a piece of paper so that you can play along while I am explaining how to complete the puzzle.

Step 1

By far the easiest, and most obvious, way to start is to check to see if there are any lines, rows, or 3×3 boxes that have only one number missing. In general, this happens with smaller Sudoku 4×4 and Sudoku 6×6 puzzles, but you never know your luck. If there are any rows, columns, or 3×3 boxes with only one number, just insert the one that’s missing; it’s as easy as counting from 1 to 9.

However, unless you are doing Very Easy Sudoku 9×9 puzzles, the chances of having only one number missing is slim. Having said that, we can use a mini version of this step for 3×3 boxes, which you will see later. Anyway, if there are no single empty squares with the puzzle you are doing, then you will need to go to Step 2.

Step 2

Actually, there are numerous Step 2s you can do and there is little difference between them. Here, I’m going to show what I do first but as you become more skilled in the art of Sudoku solving, you may find that you prefer a different method. Personally, I like to concentrate on 3×3 boxes first. Take a look at Fig. 1 below:

Figure 1

Let’s concentrate on Columns 4 – 6. Let’s start with ‘1’. We can see that there is a ‘1’ in both Columns 4 and 6, which means that we need to put a ‘1’ in Column 5 of the bottom middle 3×3 box. And you can see in Fig 1 that there is only one place ‘1’ can go because there is only one empty square. That’s the mini version of Step 1 I talked about earlier.

Step 3

Now, you could continue to concentrate on the three middle columns OR you could look at the puzzle as a whole and see if you can put ‘1’ anywhere else. I prefer to do the latter but it is totally up to you.

As it turns out, it’s possible to put ‘1’ in the top left-hand 3×3 box, the top right-hand 3×3 box, and the middle right-hand box, so we have put in ALL the ‘1s’ pretty much immediately and with very little effort. See Fig. 2 below:

Sudoku 9x9 Puzzles
Figure 2

Step 4

Check out Fig 3 below. You can see that I have highlighted the ‘2s’. You can see that there is ONE obvious place to put one of the ‘2s’. Can you see it? I already put it in to speed things up a bit. Unfortunately, there are no more obvious places, so what to do?

Figure 3

If you now look at Fig 4 below, you can see what I did. I pencilled in the remaining ‘2s’ to see if they would help me. When you are more experienced (I’m assuming you are new to Sudoku puzzles or you wouldn’t be reading this), you will be able to ‘see’ these without having to pencil in clues, but I did this just to show you how this method can help.

Figure 4

As you can see, there is only one possible place to put ‘2’ in the middle left-hand 3×3 box, which means you can also put ‘2’ in the bottom left-hand box. The other pencilled in clues can’t be solved yet, so we’ll leave them as they are for the moment.

Step 5

Now, let’s look at #3 and Columns 4 – 6 again. Columns 4 – 6 don’t have #3 and if we look round the puzzle, there’s only one obvious square we can do. Check out the bottom left-hand 3×3 box and you can see that it helps us place ‘3’ in the bottom middle 3×3 box. This, let’s us also place a ‘3’ in the bottom right-hand 3×3 box.

I called this ‘Step 5’ because we’re going to use another technique to help us. Look at Fig 5 below and you will see where we are at with #1, #2, and #3 so far. You will see that we can’t place a ‘3’ in the top middle 3×3 box so I did some pencilling in.

Figure 6

As you can see, we don’t have a solid answer for the top middle 3×3 box but because the two pencilled in ‘3s’ are in a line, we know where the ‘3’ goes in the top left-hand 3×3 box. Pretty cool, right?

Now, check out the middle middle 3×3 box. I could have pencilled in the possible positions for ‘3’. However, because there are three possible places that ‘3’ could go, I don’t personally like this. I think that if you pencil in more than TWO clues, the puzzle becomes messy and difficult to follow.

If you check out Fig 5 above, you will see that I have erased the pencilled in ‘3s’. As there is no pencilling in, what this tells me is that, unlike the other two 3×3 boxes containing pencilled in ‘3s’, the middle box has more than two places the ‘3’ can go. That doesn’t make it bad, of course. It’s purely a choice I make to keep the puzzle uncluttered.

Step 6

I’ve called this ‘Step 6’ but really it is just a return to Step 1. In fact, by now, we will almost certainly rotate between Steps 1 and 5 until we have finished. Let’s see if that’s true.

Let’s look at #4 and the middle 3 columns yet again. We can see that we know where the ‘4’ goes in the bottom middle 3×3 box, and we can place the ‘4’ of the middle 3×3 box by pencilling in the ‘4s’ in the middle left-hand 3×3 box. I have also pencilled in the ‘4s’ in the bottom right-hand 3×3 box but, following my rule of not cluttering up the puzzle, I have left top and bottom left-hand 3×3 boxes alone.

Figure 7

Step 7

Moving on to ‘5’ and to mix things up a bit, let’s pencil in the ‘5s’ in the top left-hand 3×3 box. Because we did that, we can put ‘5’ into the top middle 3×3 box, the top right-hand box, the bottom right-hand 3×3 box, and the middle left-hand 3×3 box. And because of all that, we can now put in the ‘5’ in the top left-hand 3×3 box that we originally pencilled the clues into. Neat, huh? Look at Figure 8 below to see the result.

Sudoku 9x9 Puzzles
Figure 8

Step 8

Now, if you look at the bottom middle 3×3 box, we have finally got the opportunity to do a Step 1 here as it only has one empty square, so we can put ‘8’ in it. Look around and see if you can complete all the other 3×3 boxes with the ‘8’. Did you notice anything unusual?

You may have noticed that the bottom right-hand 3×3 box had only ONE pencilled in ‘4’. If you did, I hope you filled in the square and then checked out if you could put ‘4’ anywhere else. If you did, you should have a puzzle that looks something like this.

Figure 9

Notice that I didn’t fill in all the ‘4s’ because I wanted to point out another technique which will help you when you are doing more difficult Sudoku puzzles. Look at Fig 7 above and concentrate on Columns 1 – 3. You will see that I have pencilled in ‘4s’ in the top 3×3 box, the middle 3×3 box, and the bottom 3×3 box.

However, in the top and middle boxes, the ‘4s’ are both in Columns 2 and 3. This means that in the bottom 3×3 box, the ‘4’ must be in Column 1 and that means there is only one place it can go. So, we now have this:

Figure 10

Step 9

I don’t think there is any point in going on. I am absolutely sure you can finish the rest of the puzzle on your own. Carry on with number 6 using all the techniques above and you should have few problems. Try it now and then take a look at the image below.

Sudoku 9x9 Puzzles
Figure 11

Wrapping It All Up

And there you have it. I hope you found that useful, especially if you are new to Sudoku puzzles. While there will (eventually) be instructions for other Sudoku puzzles on this website, the steps above more or less hold true for ALL standard Sudoku puzzles (4×4, 6×6, 9×9, 12×12, and 16×16).

Additionally, I just want to point out that there are many ways to solve Sudoku puzzles and that some of the possible techniques that can be employed were not mentioned above. That’s not because I have an issue with them (that would be weird). I didn’t mention them because I didn’t need them when solving the puzzle we looked at together.

As you get more experienced, I am sure you will come up with your own little ways of helping you complete Sudoku puzzles and that’s great! The steps above are just to get you started. The rest is very much up to you.

And that really is it. Don’t forget that I make many different Sudoku puzzle books that can all be found on my Amazon Author‘s Page. Feel free to buy as many as you want! 😉

Finally, thank you for reading this and don’t forget to tell your friends!

Giles Ensor

Teacher, writer, and dad who spends most of his time making many different types of Sudoku puzzles (and other puzzle books when he finds time) because a mental workout is just as important as a physical one.

View all posts by Giles Ensor →

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