How to print Sudoku puzzles

Printable Sudoku at a difficulty that means something, with a guarantee of a unique solution.

Generate puzzles for a newspaper-style page, a classroom, or a long journey, several to a sheet with answers on their own page.

Step-by-step

1. Choose a difficulty.
2. Choose how many puzzles per sheet.
3. Generate and print.

What the difficulty setting means

It is the hardest technique required, not the number of givens. Easy puzzles fall to scanning alone. Medium needs hidden singles. Hard requires pairs and pointing pairs. Expert needs an X-wing or similar.

This is more honest than counting clues. Clue count correlates only loosely with difficulty — a 26-clue puzzle solvable by scanning is easier than a 30-clue puzzle needing an X-wing — and grading by technique is why the ratings here behave consistently.

Unique solutions, always

Every puzzle is verified to have exactly one solution before it is offered. A puzzle with two cannot be solved by reasoning, only by choosing arbitrarily, and handing that to somebody is a waste of their afternoon.

Printing

Grids are sized for comfortable pencil work — enough room for candidate marks, which the harder levels require. Print in black and white; nothing depends on colour. Answers start a fresh page.

Difficulty is not the number of clues

It is natural to assume fewer givens means a harder puzzle, and it is not reliably true. A twenty-four clue grid can be gentle and a thirty clue grid can be a grind, because difficulty comes from which solving techniques the grid forces you to use rather than from how much is filled in.

A puzzle solvable entirely by scanning — looking along rows and columns for the only place a digit can go — is easy however sparse it looks. One that requires you to hold candidate sets in mind and spot a pair, a triple or an X-wing is hard however generous it looks. Grading by technique is the only method that matches how a puzzle actually feels, which is why clue count is a poor label and the bands here are named for what you have to do rather than for what you are given.

One solution, or it is not a sudoku

A proper sudoku has exactly one solution. This is not a stylistic preference: without it, solving stops being deduction and becomes choosing, and two solvers can both be right and disagree.

Puzzles with multiple solutions turn up surprisingly often in the wild, usually from a generator that removed clues without re-checking, or from a person building one by hand. The classic symptom is reaching a position where two digits could be swapped in four cells forming a rectangle with nothing to distinguish them — an unavoidable rectangle, and a sign the puzzle is broken rather than that you have missed something. Any generator worth using verifies uniqueness after every clue it removes, and puts the clue back when uniqueness fails.

Frequently asked questions

Are these puzzles always solvable without guessing?

Yes. Each is verified to have a single solution reachable by the documented techniques.

What is the difference between hard and expert?

Hard needs pairs and pointing pairs. Expert needs a technique like an X-wing, where you reason about a digit's possible positions across two rows and two columns at once.

Can I print several to a page?

Yes, and answer keys are collected on their own page so a sheet can be handed out intact.