How to Improve at Sudoku - Step Up from 4x4 and 6x6 to 9x9

If Sudoku leaves you feeling stuck, the first thing to question is not your ability but the size of the grid you started on. A 9x9 board holds 81 cells, and solving it means tracking three constraints at once - row, column and block - while holding nine possible digits in your head for every empty cell. For someone who has just learned the rules, that volume of information is the obstacle in itself. No mental room is left for reasoning, so digits get guessed, the grid collapses, and the conclusion becomes 'this puzzle is not for me'. Whenever a skill is learned in stages, the standard approach is to strip away everything except the one thing you are trying to master. In Sudoku, stripping away means shrinking the grid. A 4x4 has 16 cells; a 6x6 has 36. The structure of the constraints stays exactly the same, so the practice loses none of its substance. The only thing that shrinks is how much you must track at once. Learn the rules and the feel of a forced cell on 4x4, learn scanning and pencil marks on 6x6, and let 9x9 be about nothing but the width of the board. It looks like a detour, but this order gets you there sooner. Start by settling the basic rules of Sudoku, then pick up a small grid.

A 4x4 places the digits 1 to 4 across four 2x2 blocks. With so few cells to fill, even a first attempt is over in a couple of minutes. Two things are worth taking from this stage. The first is repetition until checking three directions - row, column, block - happens as a reflex rather than a decision. The second is knowing what a forced cell feels like. In the diagram below, consider the top-left cell. Its row already contains 2 and 3, and its column already contains 3 and 4. Remove what the row and column forbid and only 1 remains; there is nothing to guess. That line of reasoning - nothing else fits, so it must be this - is the foundation under every Sudoku technique, at any grid size. If you build the habit on 4x4 of stating your reason before writing a digit, the dead ends you hit on 9x9 will be far shallower. The move does have a name, the naked single, but the feel in your hand matters more than the label. Once you can finish ten or so 4x4 puzzles with a reason for every entry, this stage has done its job.

Once a 4x4 takes you only a few minutes, move to 6x6. Here six wide 2x3 blocks sit side by side, and rows, columns and blocks overlap in busier ways than on 4x4. The skills to pick up are the order in which you look at the board, and how to use pencil marks. There are two ways to look. You can pick a cell and narrow down which digits could go in it, or pick a digit and hunt across the whole board for where it could go. The second one comes into its own on 6x6. Work through 1 to 6 in turn, striking out the rows and columns that already hold each digit, and a block emerges where only one square can take it. That scan barely earns its keep on 4x4; on 6x6 it is plainly the difference in speed. As for pencil marks, a 6x6 cell has at most six candidates, which is a quantity you can actually write down - a comfortable size for practice. There is no need to fill every cell with candidates; start by noting only the cells you have narrowed to two. The notation habits for pencil marks are worth borrowing wholesale. For the character of the 6x6 board itself, and why rectangular blocks change how you see it, see the guide to 6x6 mini Sudoku.

Judge the move by the quality of your dead ends rather than by the clock. You finish an easy 6x6 without once falling back on a guess. When that happens two or three times in a row, 9x9 is fair game. If guessed digits still appear anywhere, a bigger grid will only bring you to the same wall, so keeping the order costs you less time overall. What trips people on their first 9x9 puzzles is usually not technique but field of view. Try to take in 81 cells at once and your eyes slide over the board with no decision about where to begin. The fix is simply not to look at the whole board. Pick one row, column or block that is already well filled and work it exactly as you worked a 6x6. Densely filled areas carry the strongest constraints, so forced cells surface quickly. Fill one and the constraints around it tighten, which reveals the next. Getting onto that chain is the first wall; once you are on it, everything you built on 6x6 applies unchanged. For the first few weeks, choose only puzzles with plenty of givens. Begin with the easy 9x9 puzzles and raise the difficulty only after 'finished it without guessing' has become the norm.

Frequency beats duration. Fifteen minutes every day settles the scanning routine into your hands more thoroughly than a single two-hour session. The table below gathers, for each stage, how long to spend, what to keep in mind, and the sign that says move on. Treat the times as rough guides; whether you finished without guessing matters more than how fast you were. A practical way to structure one session is to spend the opening minutes one stage below where you are. Even while you are working on 9x9, solving a single 4x4 or 6x6 first means you start the main puzzle with the scanning routine already fresh. Mini Sudoku you can play in the browser (4x4 and 6x6) lets you take one puzzle on the spot with nothing to set up, which suits this warm-up well. It is a beginner-friendly page, so it also works for a child's practice or as a brain exercise for an older family member. If you prefer to think with a pencil in hand, or want the family working the same puzzle, use the printable puzzles. Screen and paper differ in how easily you can jot candidates and in how your eyes tire. Try both and make the one you will keep doing your main habit.

Measure yourself on solving time alone and the inevitable plateau will break your resolve. Times swing by a factor of two or more at identical skill, because so much depends on how a puzzle was built. Four signs are worth watching together. The first is the share of puzzles you finished without guessing; progress shows up here more honestly than anywhere else. The second is how long it takes to find your next move after getting stuck. The number of stuck moments falls only slowly, but recovery time shortens reliably with practice. The third is how often you erase a digit you had written. Fewer corrections means the habit of confirming a reason before writing has taken hold. The fourth is whether you can explain your path once the puzzle is done, because a puzzle you can explain is one you can reproduce when a similar position appears. Keep the record plain: the date, the grid size, a yes or no on whether you guessed, and a note on where you stalled. One line with those four items is enough, and within a fortnight your own tendencies become visible. Reading the difficulty labels against the levels of Sudoku difficulty makes your entries easier to compare with one another.

Some weeks after moving to 9x9, a stretch arrives where nothing seems to get easier. Pushing the difficulty higher here mostly just drains you. The useful direction is the other one: spend a week back on 6x6, and on 4x4 if needed. This is not a retreat. A small grid lets you see your entire procedure at once, which makes obvious whatever you have been skipping. Missing a column mid-scan, pressing on without noting cells that were down to two candidates - habits like these are hard to catch at any other scale. What you are checking during that week is not speed but gaps in procedure. Are you scanning 1 through 6 all the way? Are you entering from the densely filled areas? Can you say the reason before you write? Solve a dozen puzzles with those three in mind, return to 9x9, and the dead ends are usually shallower than before. For untangling a dead end itself, see recovering when you get stuck. Once you can move up and down the stages at will, Sudoku becomes a pastime you can keep for years: days for hard puzzles, days for tidying your procedure on a small grid, chosen by how you feel.