Mini Sudoku Rules: The Complete 6x6 Beginner's Guide

The grid

A Mini Sudoku board is 6 cells wide and 6 cells tall — 36 cells in total, roughly a third the size of a Classic 9x9 grid. Those 36 cells are also split into six 2x3 boxes (two columns wide, three rows tall), each outlined with a bolder border so you can spot it at a glance. Every puzzle starts with some cells already filled in as clues; your job is to complete the rest.

The three rules

Every Sudoku variant, Mini included, comes down to one idea applied three times over. Fill the grid with the digits 1 through 6 so that:

• • Each row (reading left to right) contains 1–6 exactly once — no repeats.
• • Each column (reading top to bottom) contains 1–6 exactly once — no repeats.
• • Each 2x3 box contains 1–6 exactly once — no repeats.

All three rules apply at the same time, independently. A digit can't repeat in its row even if it's sitting in a different box; it can't repeat in its box even if it's in a different column. The puzzle is solved the moment every cell is filled and all three rules hold everywhere on the board simultaneously — and a well-formed puzzle always has exactly one solution that satisfies all of them.

What Mini Sudoku is not

It's easy to assume a number puzzle involves math, but Mini Sudoku doesn't ask you to add, subtract, or compare digit sizes anywhere. The numbers 1 through 6 are really just six distinct symbols — you could swap them for six colors or six letters and the puzzle would play identically. That's different from a variant like Killer Sudoku, where cages add a real arithmetic constraint on top of the standard rules. Mini Sudoku is pure placement logic, which is exactly why it's such a clean way to learn.

A worked example

Rules are easiest to internalize by watching them solve something. Look at the highlighted row, column, and box in the image above: the row already contains 4, 1, 2, and 6, leaving only 3 and 5 unplaced. The column already contains 5 and 1, leaving 2, 3, 4, and 6 unplaced. And the highlighted box already has 2 and 6 filled in, leaving 1, 3, 4, and 5 unplaced.

That's the entire technique beginners need for most of a puzzle: look at a row, column, or box that's nearly full, list which digits are missing, then check the empty cell's other row/column/box to see which of those missing digits is still allowed there. Once only one candidate survives all three checks for a cell, that's your answer — place it and move on to the next nearly-complete line. Puzzles get harder when fewer lines are "nearly full" at the start, which is exactly what the difficulty levels below control.

Want the full technique library, including what to do once single-candidate cells run out? Our solving techniques guide covers scanning, naked pairs, and more — all directly transferable from Mini to Classic Sudoku.

Notes (pencil marks)

When a cell has more than one possible digit left, you can toggle notes mode and tap each candidate into the cell as a small reminder, rather than trying to hold every possibility in your head. Notes are just scratch space — they don't have to follow the row/column/box rule themselves, and you can add or remove them freely as you narrow things down. Only the final digit you commit to a cell needs to satisfy the puzzle's rules. Most Easy and Medium Mini Sudoku puzzles can be solved without ever opening notes; they tend to earn their keep once you're a few moves into a Hard puzzle.

Difficulty levels

Difficulty is controlled by how many of the 36 cells are given to you as starting clues — fewer clues means more deduction before a cell becomes certain:

Common rule mix-ups

• • "It's in a different box, so it's fine" — it isn't, if it repeats in the same row or column. All three rules apply at once, not one at a time.
• • Confusing notes with answers — a candidate number jotted as a note isn't committed yet, and won't trigger a conflict warning the way a placed digit will.
• • Expecting a "6x6 box" — boxes in Mini Sudoku are 2 columns by 3 rows (or vice versa depending on orientation), not a 3x3 square like Classic Sudoku's boxes.
• • Treating digits as values — there's no addition or comparison involved; 6 isn't "more" than 1 for solving purposes, they're just six distinct labels.

Frequently asked questions