The first challenge in sudoku is often not doing the arithmetic. It is knowing where to look. If you are staring at a 9×9 grid and every empty cell looks the same, a smaller puzzle lets you focus on one deduction at a time.
Start with a 4×4 grid
A 4×4 sudoku uses the numbers 1 through 4. Each row, column, and 2×2 box must contain each number once. There is no adding; the rule is simply that a number cannot repeat.
This example is almost solved so you can focus on one cell. Which number belongs in place of the question mark?
Show the deduction
The first row already contains 1, 2, and 3, so it is missing 4. The last column contains 2, 3, and 1, so it is missing 4 as well. The top-right box contains 3, 1, and 2, so the 4 fits. We did not try a number at random; we found the only number that can go there.
A routine for deciding where to look
- Find an area with few empty cells. It might be a row, column, or box. The more numbers already placed, the fewer possibilities you need to compare.
- List what is missing. Then check which numbers the other two crossing areas rule out for each cell.
- Write only when you can explain why. “This row needs a 4, and no other number fits here” is a deduction. “I’ll try a 4” is a guess.
How to use a hint without losing the challenge
Before looking at the complete solution, try to get a smaller nudge: the area to inspect or the number worth focusing on. Return to the grid and work through the reasoning yourself.
When to move to a larger sudoku
Once the rules feel familiar, try a 6×6 grid using numbers 1 through 6 and boxes that are two rows by three columns, or three rows by two columns, depending on the layout. Then move to 9×9 with 3×3 boxes. The no-repeats rule stays the same; there is simply more information to observe.
Grid size alone does not determine difficulty. The point of this progression is to get comfortable with the rules before facing a board with more cells.
For a next step, explore how to note and update candidates, or see six common mistakes and how to correct them.