Puzzle Desk › Sudoku › Printable › Hard
Hard Sudoku to print
Eight puzzles from our Tough level, picked from 200 new ones because they lean hardest on advanced steps. None of them can be finished with singles and pairs alone, and none needs guessing.
- 8 puzzles: 8 Tough
- A4 and US Letter
- Answers in their own file
- Ids S-T5 to S-T12
What’s in the pack
One per page, the grid is 15 cm square with 24 pt digits: room to pencil in candidates. Four per page, each grid is 8.4 cm with 14 pt digits. The answer key prints six answers per page.
| Id | Level | Givens | Beyond singles, our solver needed |
|---|---|---|---|
| S-T5 | Tough | 28 | XY-wing ×3 |
| S-T6 | Tough | 26 | Naked triple, X-wing, XY-wing |
| S-T7 | Tough | 30 | XY-wing ×3, X-wing |
| S-T8 | Tough | 30 | X-wing ×2, XY-wing ×2 |
| S-T9 | Tough | 28 | XY-wing ×3, Hidden triple |
| S-T10 | Tough | 26 | X-wing ×2, XY-wing ×2 |
| S-T11 | Tough | 28 | XY-wing ×4, Naked triple |
| S-T12 | Tough | 26 | XY-wing ×6, X-wing |
How hard is hard?
What “hard” means here
These are Tough puzzles, the hardest of our three levels. We grade by the hardest technique a logical solver needs, not by the number of givens: a Tough puzzle can’t be finished with singles, pairs and pointing pairs alone, and needs at least one X-wing, XY-wing, swordfish or triple. Every one has exactly one solution and was solved by logic, with no guessing.
X-wing
A digit that fits in only two cells of one row and two cells of another, in the same two columns, must sit in opposite corners of that rectangle, so it can be crossed off the rest of those columns.
XY-wing
A cell with two candidates, say 3 and 7, that sees a 3/5 cell and a 7/5 cell: one of those two must be 5, so 5 goes from any cell that sees both of them.
Triples
Three cells in a row, column or box that share just three candidates between them: those digits can be crossed off everywhere else in that unit.
How to play and print
The rule
Fill every empty square so that each row, each column and each 3×3 box holds the digits 1 to 9 once. The givens never move. Each puzzle has one solution, and you can reach it by reasoning, without guessing.
Getting started
Look for a row, column or box that is nearly full, or a digit that already appears often. Pencil small candidates into the corners of a cell when you are not sure yet.
Printing
Choose the PDF for your paper and print at 100% (“Actual size”), portrait. The sheets are black on white and print well in greyscale. The answer key is a separate file, so you can hand out puzzles without the answers.
Using the sheets
Free to print for personal, classroom and library use. Please don’t sell or republish the sheets. No sign-up, no email: the links above are the files. Each sheet carries its id, so a class can check answers by id.