Mini Sudoku: How to Think Through a 6x6 Grid

The rules take one line. Fill the grid so every row, every column, and every 2x3 box holds the numbers 1 to 6 exactly once.

What that line hides is that a 6x6 is not a shrunken 9x9. The box shape changes the arithmetic underneath, and people who arrive with 9x9 habits usually end up working harder than they need to.

Why the box shape matters

Each box is two rows tall and three columns wide, and two things follow from that.

A row passes through only two boxes, so filling three cells of a row says something loud about both of them. A column passes through three boxes but touches only two cells of each, which makes columns the tighter constraint of the two. A column with three numbers in it is often one move from finished, and most people look at it last.

On a 9x9 you scan for a digit across nine units. Here there are six of everything, and every unit you touch overlaps two or three others, so a single placement travels further than it would on a big grid. That is why a Mini Sudoku can look half empty and then collapse in four moves.

Count before you read

Reading the grid left to right is the slow way in. Count instead.

Find the number that already appears most often and hunt for where it has to go next. If 4 is placed three times, the rows and columns holding those 4s become forbidden ground, and the boxes that are left usually have one legal cell between them. On Monday and Tuesday that single habit carries you most of the way to the end.

While you are scanning, two things are worth catching. A row, column, or box with five numbers in it has exactly one answer left, which sounds too obvious to miss and gets missed constantly. The other is the move solvers call a hidden single: take a unit and a number, and if every empty cell in that unit is blocked from holding it except one, that cell is settled. The hidden single keeps earning its keep all week.

When scanning dries up, start pencilling

From Wednesday on you will hit a point where counting turns up nothing. That is the puzzle working as designed.

Switch on notes and mark candidates for the cells that look tightest, usually whatever sits in the fullest row or box. Pencilling the whole grid is rarely worth it on a 6x6; you mostly create a mess you then have to maintain.

Two patterns repay the effort. A pair is two cells in the same unit that come down to the same two numbers. You will not know which cell takes which, but you know both numbers are spoken for, so you can strike them from every other cell in that unit. On a six-cell row, clearing two candidates out of the remaining four is usually decisive.

The other is a number trapped in a line. If a number can only sit in cells that share a row inside one box, it lives somewhere in that row and nowhere else in it, which means you can knock it out of the row's other box. That move breaks more Friday and Saturday grids than anything else in the toolkit, and it repays training your eye for the shape.

About those red cells

Clashes turn red the moment you make one. They are there to catch a slip. Using them to explore is guessing with extra steps, and it spends lives you may want later.

Every board can be finished by reasoning alone, so if you find yourself testing rather than deducing, the move you want exists and you have not found it yet. When you genuinely cannot see it, the fastest recovery is to stop staring at the cell and re-scan a different number from scratch. Fixation costs more minutes on a small grid than any technique saves.

What changes as the week goes on

The rules never change and neither does the grid size. What changes is how much you get for free. Early in the week most cells fall to scanning. Later, fewer do, and the pencil work starts earlier. By the weekend, expect at least one moment where you need a pair or a trapped number before the board moves again. The day-by-day breakdown, including how long each day should take, is in how the daily week works.

If you want more of those moments on demand, the practice library has thousands of full-size sudoku boards across five difficulty tiers, plus the variants: killer, jigsaw, samurai, and more.

Frequently asked questions

Is a 6x6 sudoku easier than a 9x9?

Usually faster. Not always easier. There is less grid to fill, but the constraints are tighter and the deductions chain more quickly, so a hard 6x6 can demand the same techniques as a hard 9x9 in a fraction of the space.

Do I need pencil marks to solve it?

Not on the gentler days. From midweek on they save more time than they cost, especially for spotting pairs.

What if I get stuck?

There is always a findable next move. Re-scan from a different number rather than staring at the same cell, and check the fullest column before anything else.

Can I ever be forced to guess?

No. Every board is checked by a separate program before publication to prove it has exactly one solution reachable by logic. If a board needed a guess, it never reached you.