Printable
Hard printable Sudoku
About 29 givens. Hidden singles do most of the work here, and roughly one puzzle in five asks for more than that. Keep a pencil and eraser handy.
Free to copy: schools, libraries, care homes and clubs may reproduce and hand out these sheets at no cost.
Why hard puzzles feel different
With less than a third of the cells given, you have to search with intent: which number has only one place left in a row, column or box? For most hard puzzles, that question carries you through the whole grid.
About one hard puzzle in five reaches a point where even that runs out. Then candidate lists and patterns such as naked pairs help, ruling numbers out of other cells.
Pencil marks on paper
Write candidates small in the corners of each cell, always in the same spot – 1 top left, 9 bottom right. Pairs and patterns then stand out at a glance. Two or four puzzles per page leave enough room for it.
Always solvable, never a guess
Every puzzle is checked for exactly one solution when it's generated. If you're stuck, you're missing a technique, not luck. The answer page at the end shows the givens in bold and the numbers you were looking for in a lighter tone.
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More: Kids’ Sudoku· Blank grid· 4 per page· 6 per page
Rules · Techniques · Play