Printable sudoku
A 4 by 4 sheet for beginners and a full 9 by 9 puzzle, both with a unique solution and the answer key on the second page.
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Sudoku
Name: ______________________ Date: ______________
4 by 4 — for beginners
| 2 | 3 | 3 | 2 |
| 4 | 1 | 4 | 1 |
| 4 | |||
| 3 | 4 | 2 |
9 by 9 — the full thing
| 7 | 8 | 8 | 3 | |||||
| 1 | 6 | 5 | 1 | |||||
| 4 | 4 | |||||||
| 1 | 8 | 8 | 4 | |||||
| 3 | 8 | 1 | 8 | 1 | 6 | |||
| 7 | 2 | 4 | 2 | 7 | 3 | 6 | ||
| 7 | 5 | 8 | 1 | 1 | 2 | |||
| 4 | 7 | 7 | 5 | |||||
| 4 | 6 | 2 | 5 | 2 | 4 |
Every row, every column and every outlined box must contain the digits 1 to 9 exactly once. A printed sudoku is best done with a pencil, so you can change your mind.
Sudoku — solution
Both puzzles have exactly one solution.
4 by 4
| 2 | 3 | 3 | 2 |
| 4 | 1 | 4 | 1 |
| 4 | 2 | 1 | 4 |
| 3 | 3 | 4 | 2 |
9 by 9
| 7 | 8 | 9 | 8 | 8 | 3 | 1 | 3 | 7 |
| 1 | 6 | 9 | 8 | 9 | 5 | 1 | 2 | 5 |
| 4 | 4 | 9 | 4 | 6 | 2 | 4 | 3 | 5 |
| 3 | 3 | 1 | 6 | 1 | 4 | 8 | 8 | 4 |
| 3 | 8 | 1 | 8 | 6 | 4 | 4 | 1 | 6 |
| 7 | 2 | 4 | 2 | 1 | 7 | 7 | 3 | 6 |
| 7 | 3 | 5 | 8 | 8 | 1 | 5 | 1 | 2 |
| 9 | 2 | 4 | 3 | 7 | 3 | 7 | 2 | 5 |
| 4 | 6 | 8 | 9 | 2 | 5 | 2 | 4 | 3 |
What is on the sheet
- A 4 by 4 grid with four 2 by 2 boxes - small enough for a child and for a short attention span.
- A full 9 by 9 grid with the nine outlined boxes, generated with a unique solution so there is no guessing.
- The name and date line at the top, and the answer key on the second sheet.
How to print
- Print at 100 percent. A "fit to page" setting makes the cells too small to write in.
- Use a pencil, not a pen. Most people change a mind at least once, and a printed sheet is cheap to redo.
- Print the 4 by 4 on its own for a young child, and the 9 by 9 for anyone who wants a real puzzle.
- Photocopy as many as you need for a class. No attribution is required on the copy.
How to solve the 9 by 9 without guessing
Work in one pass rather than filling the whole grid row by row, and look for cells that have only one candidate left. Scan each row for a digit that appears eight times - its only home is the empty cell, and that is a free placement. Then do the same for each column, then for each box. When no single candidate is left anywhere, look for a digit that has exactly two possible homes in a row, a column or a box and place it in both if they are forced. Only when all of that runs out is a guess worth making, and by then there is usually only one cell left that could take two values.
The 4 by 4 is worth trying first for a child, because the same logic finishes it in about a minute and teaches the idea without the tedium.
Sudoku on a screen
The sudoku game has three difficulties, highlights conflicts as you type, and can explain a hint rather than just giving you the number. There is also a daily sudoku that is the same puzzle for every player on a given day, with a streak counter.