Sudoku Variations: Mini, Diagonal, Killer and More

The Sudoku most of us know is the classic one: a 9 by 9 grid, nine boxes, and the numbers 1 to 9. That is the game we offer here. But open a book of puzzles and you will soon meet its cousins, with smaller grids, crooked boxes, extra rules or even a little arithmetic. This page explains the ones you are most likely to come across, so that none of them takes you by surprise. First, the choices you have in our own game.

Ways to Play Classic Sudoku on This Site

Easy, Medium and Hard

Our three levels are graded by the reasoning a puzzle needs. An Easy puzzle can be finished one square at a time. A Medium puzzle needs pairs or pointing somewhere along the way. A Hard puzzle needs triples or a pattern that crosses the grid. The strategy guide explains each of these. All levels have exactly one solution and never need a guess.

With or without mistake marks

In Settings you can choose whether the game tells you right away when a number is wrong. With the marks on, a wrong number turns red and gets an underline and a cross. This is the gentle way to learn, and it is on by default for Easy puzzles. With the marks off, the game stays quiet, as a puzzle on paper would. Many solvers find that more satisfying once they know the ropes. Hint will still find a wrong number for you if you ask.

Square first or number first

Most people tap a square and then choose its number. Some prefer the reverse: choose a number, then tap every square where it belongs. The second way suits solvers who work through all the 1s, then all the 2s, and so on. Both work at any time, and Settings lets you make number-first the usual way.

The Daily Puzzle and numbered puzzles

The Daily Puzzle is the same for everyone on a given date, with one grid for each level. Every other puzzle has a number too, from 1 to 999,999. Type a number in Settings to play that exact puzzle, or to play the same one as a friend.

With or without a clock

The timer is hidden unless you switch it on. There is never a time limit. If you like to race yourself, turn it on and your time is shown when you finish.

Smaller and Larger Grids

Mini Sudoku: 4 by 4 and 6 by 6

A 4 by 4 grid uses the numbers 1 to 4 and has four boxes of four squares. It takes a minute or two and is a lovely way to teach the idea to a grandchild. The 6 by 6 version uses 1 to 6 with boxes two squares tall and three wide. The rule is the same as always: no repeats in any row, column or box.

Giant grids: 12 by 12 and 16 by 16

At the other end are grids that use the numbers 1 to 12 or 1 to 16, sometimes with letters standing in for the numbers above 9. They need no new methods, only a great deal more patience and a sharp pencil. A 16 by 16 puzzle can fill a whole evening.

Same Grid, One Extra Rule

Diagonal Sudoku

The grid looks like a classic one, but the two long diagonals, from corner to corner, must also hold 1 to 9 once each. The extra rule gives you two more lines to scan, so these puzzles are usually printed with fewer starting numbers.

Extra-region Sudoku

Four shaded 3 by 3 blocks are laid over the grid, each sitting across the corners of the normal boxes. Each shaded block must also hold 1 to 9. As with the diagonal kind, more regions mean more clues to work with and more places to look.

Odd-even Sudoku

Some squares are shaded to show that they hold an even number (2, 4, 6 or 8), or marked to show an odd one. That halves the choices for those squares before you begin.

Different Shapes

Irregular Sudoku

The nine neat boxes are replaced by nine wiggly regions of nine squares each, fitted together like the pieces of a jigsaw. Rows and columns work as usual, and each region must hold 1 to 9. Scanning takes more care, because a region can wander across four or five rows. If you like the look of interlocking shapes, you may also enjoy our jigsaw puzzles.

Five-grid Sudoku

Five classic grids overlap in the shape of an X: one in the middle and one on each corner, each sharing a box with the middle grid. Every grid must be solved by the classic rule, and the shared boxes have to satisfy two grids at once. You often need to go back and forth between grids to make progress. These are long puzzles, best suited to a rainy afternoon.

Sudoku with Arithmetic

Killer Sudoku

This is the one variation where sums matter. The grid usually starts completely empty. Dotted outlines group the squares into "cages," and each cage shows a small total. The numbers in a cage must add up to that total, and a number can't repeat inside a cage. The classic rule for rows, columns and boxes still applies.

The way in is to learn a few sums that can be made only one way. A two-square cage totaling 3 must be 1 and 2. A two-square cage totaling 17 must be 8 and 9. A three-square cage totaling 6 must be 1, 2 and 3. It also helps to remember that every row, column and box adds up to 45.

Greater-than Sudoku

Small arrow signs between neighboring squares tell you which of the two holds the larger number. Often there are no starting numbers at all. A square that is smaller than all its neighbors is likely to be a 1 or 2, and that is where you begin.

Letters and Pictures

Since the numbers in Sudoku are only nine different marks, any nine symbols will do. Letter Sudoku uses nine letters, and when the grid is finished one row or diagonal often spells a word. Children's books use nine pictures or colors. The solving is exactly the same. If letters are more your thing than numbers, have a look at our Word Search.

Which One Should You Try?

Whichever you try, the habits from the classic game carry over: scan one number at a time, use notes when two squares are possible, and never guess. The best preparation for any of them is a steady diet of classic puzzles, and those are free here, as many as you like.