How it works
This hard sudoku printable deals 9 by 9 puzzles at two levels only, Hard and Expert, two to a page so there is room for pencil marks. Each has one answer and can be solved without a guess.
Read the full guide
What Hard asks for: locked candidates
A Hard puzzle cannot be finished by singles alone. Somewhere it needs locked candidates. Pointing: inside one box, the only squares left for a digit lie in one row, so the digit comes out of the rest of that row. Claiming is the reverse: in one row, the only squares left for a digit lie in one box, so it comes out of the rest of that box. Columns work the same way.
What Expert adds
An Expert puzzle needs at least one harder step: a naked or hidden pair, triple or quad, an X-wing, a swordfish or an XY-wing.
- Easy and Medium puzzles, and the small grids, are on the printable sudoku page.
Questions and answers
What makes a sudoku hard?
The steps it needs, more than how few numbers it shows. Here a Hard puzzle has 24 to 30 squares filled in and needs locked candidates, and an Expert puzzle has 22 to 28 and needs one step beyond that.
Is this a difficult sudoku printable without guessing?
Yes. Each puzzle is graded by the hardest step a person needs, and none needs a guess. Hard needs locked candidates and nothing harder. Expert needs a pair, a triple, a quad, an X-wing, a swordfish or an XY-wing.
Why two puzzles to a page?
Hard steps need pencil marks, the small candidate digits written in the corners of a square, and two to a page leaves room for them. Per page, inside More options, also has 1, 4 and 6.
Are the answers included?
Yes. They print on their own last page as small solved grids, numbered to match, so the puzzle sheet can be handed out alone.