How to play 6x6 Killer Sudoku

Sudoku is a logic puzzle in which you fill a grid with digits so that every row, column and box holds each digit exactly once.

Fill the small grid so every cage adds up to its sum.

About 6x6 Killer Sudoku

6x6 Killer Sudoku starts with an empty six by six grid divided into cages of connected cells, each printed with its sum. The digits in a cage add up to that sum and never repeat within it, and every row, column and box of two rows by three columns holds 1 to 6 once each.

There are no givens, so the cages alone fix the answer. With only six digits to choose from, a cage allows fewer combinations than on the larger grid, and a board of mostly small cages can rate Easy.

Here every row, column and box adds up to 21 rather than 45. Take the cages lying wholly inside a box away from 21, and what is left is the total of its other cells. Two cells adding up to 3 must be 1 and 2, and two adding up to 11 must be 5 and 6.

Most cages here hold two to five cells, and a one-cell cage turns up only on the rare board the generator has to build from smaller cages. A cage can cross from one box into the next. A two-cell cage sums to anything from 3 to 11, and only 3, 4, 10 and 11 allow a single pair. Three cells adding up to 6 must be 1, 2 and 3, and three adding up to 15 must be 4, 5 and 6. A five-cell cage holds every digit but one, so 21 minus its sum is the digit it lacks. Over 1000 generated boards, about two in three rated Easy, one in seven Medium and one in five Hard.

The goal of Sudoku

Fill every empty cell so that each row, each column and each box holds every digit exactly once. The classic grid is nine by nine, with nine boxes of three by three and the digits 1 to 9; the 6x6 grid has six boxes of two rows by three columns and the digits 1 to 6. Every puzzle has exactly one solution.

How to set up Sudoku

Choose Easy, Medium, Hard or Any as the difficulty of your next new puzzle. Easy puzzles need only the simplest deductions, Medium ones also need eliminations such as pointing pairs and naked pairs, and Hard ones need techniques beyond those.

Sudoku rules

Select a cell and enter a digit. Turn on Notes to pencil in candidate digits instead; notes are reminders, not moves, and writing a digit in a cell clears its notes. Erase empties a cell, Undo takes back your last move, and Restart lays the same puzzle out again.

A digit repeated in a row, column, box or cage is marked as a conflict, and so is a full cage that does not add up to its sum. A digit that breaks no rule but is still wrong is left unmarked, unless you turn on Check entries in the settings.

Hint fills in the next cell that logic forces from your current position, or points out your first wrong entry. Hints are unlimited, but a puzzle finished after a hint, or with Check entries on, is not recorded as a win.

The full Sudoku guide, with strategy tips and common questions