Kaizen Sudoku › How to solve Sudoku
How to solve Sudoku, step by step
Every Sudoku can be solved by logic alone, without guessing. The trick is knowing which pattern to look for. This guide walks through the techniques in the order you will need them, and shows which Kaizen Sudoku level each one unlocks.
Last updated: 2026-10-07
The rules in one sentence
Fill the 9×9 grid so that every row, every column and every 3×3 box contains the digits 1 to 9 exactly once. A well-made puzzle has exactly one solution, and every puzzle in Kaizen Sudoku does.
Start with singles
A naked single is a cell where only one digit is still possible: the other eight already appear in its row, column or box. A hidden single is a digit that can go in only one cell of a row, column or box, even if that cell has other candidates.
Scan box by box for each digit from 1 to 9 and look for the one place it can go. Beginner and Easy puzzles in Kaizen Sudoku can be solved with these two techniques only.
Use notes when singles run out
When no single is left, write the candidates into each empty cell with notes. Kaizen Sudoku removes notes automatically when you place a digit in the same row, column or box, so your candidates stay correct as the grid fills up.
Intermediate techniques
- Pointing pair: if a digit's candidates in a box all lie in one row or column, remove that digit from the rest of that line.
- Box-line reduction (claiming): if a digit's candidates in a row or column all lie in one box, remove it from the rest of that box.
- Naked pair and triple: two cells in a unit with the same two candidates (or three cells with three) lock those digits; remove them from the other cells of the unit.
- Hidden pair and triple: two digits that fit in only the same two cells of a unit claim those cells; remove every other candidate from them.
Medium puzzles need pointing pairs and box-line reductions; Hard puzzles add pairs and triples.
Advanced patterns
- X-Wing: a digit appears as a candidate in exactly two cells in each of two rows, and those cells share the same two columns. The digit can be removed from those columns everywhere else.
- Swordfish: the same idea across three rows and three columns.
- XY-Wing: three cells with two candidates each form a pivot and two pincers; any cell seen by both pincers cannot hold their shared digit.
Expert puzzles call for X-Wing and Swordfish, and Legend puzzles for XY-Wing and beyond.
Practise with the right level
Kaizen Sudoku grades every puzzle by the hardest technique it needs, so a level always means the same thing. Move up when a level starts to feel easy, and use a hint when you are stuck: it fixes a wrong number first, and otherwise fills in the next cell that can be found by logic, so you can work out why it goes there.