How to Play Sudoku for Beginners: Rules and First Steps
To play Sudoku you fill a 9×9 grid so that every row, every column and every 3×3 box contains the digits 1 to 9 exactly once. That is the entire rulebook. There is no arithmetic and no guessing: a proper puzzle has one solution, reachable by logic alone. Beginners should learn one technique first — ask where a digit goes in a box, not what fits in a cell — and everything else follows from it.
This guide takes you from never having touched a grid to finishing easy puzzles reliably. Rules, the first three techniques, a worked first move, the mistakes every beginner makes, and answers to the questions people actually ask. If a grid beats you, our free Sudoku solver shows the full solution instantly.
The rules, in full
A standard Sudoku is a 9×9 grid divided into nine 3×3 boxes. Some cells already contain digits — these are the givens or clues, and they never change. Your job is to fill every empty cell.
There are exactly three constraints:
- Every row of nine cells contains the digits 1 to 9, each exactly once.
- Every column of nine cells contains the digits 1 to 9, each exactly once.
- Every 3×3 box contains the digits 1 to 9, each exactly once.
That is all. Three rules, applied together, are enough to make the puzzle both solvable and genuinely difficult.
The vocabulary you need
| Word | Meaning |
|---|---|
| Given / clue | A digit printed in the puzzle from the start |
| Cell | One of the 81 small squares |
| Box | One of the nine 3×3 blocks |
| Unit | Any row, column or box — the three things that must hold 1 to 9 |
| Candidate / pencil mark | A digit still possible in a cell |
| Peer | Any cell sharing a row, column or box with another |
Your first technique: ask where the digit goes
Every beginner starts by picking an empty cell and wondering what belongs there. That means testing nine digits against three constraints — slow, and usually inconclusive.
Reverse it. Pick a digit and ask where it can go in a particular box. That is one digit against three constraints, roughly nine times cheaper, and it produces answers immediately.
The method has a name: cross-hatching.
- Choose a digit — say 4.
- Find every 4 already on the grid.
- Each existing 4 rules out its whole row and its whole column.
- Pick a box that still needs a 4. Count the cells that are neither ruled out nor already filled.
- If exactly one cell remains, that is the 4. Write it. If two or more remain, move to the next box — never guess.
- Continue with the same digit through every box before switching.
Your first move on a real grid
Suppose the top-left box is missing a 5, and there are already 5s in the first row and in the second column. Those two 5s strike out one row and one column of that box, leaving three cells. Not enough — move on.
Now look at the top-middle box. There is a 5 in the fourth row (irrelevant) but also one in the seventh column and one in the second row. Between them, only one cell of that box survives. That cell is the 5. Write it with complete confidence.
Then — and this is the part beginners skip — look immediately at the row, the column and the box of the 5 you just placed. Your new digit changed all three, and the next placement is very often right there.
Start with the most common digit
Before you scan, spend five seconds counting how many times each digit already appears. Start with whichever appears most.
The reason is simple. A digit that already appears seven times has only two placements left and blocks seven rows and seven columns — it is often forced immediately. A digit appearing twice blocks almost nothing, and hunting it first is close to guaranteed wasted effort.
Your second technique: the naked single
A naked single is a cell where eight of the nine digits are already blocked by its row, its column and its box. Whatever is left is forced.
To find one, pick an empty cell and read its three units. If you can account for eight different digits between them, the ninth belongs there.
Naked singles hide in the fullest parts of the grid — a row with seven digits placed, or a box with six. That is where to look. The emptiest box feels like the biggest opportunity and is almost always the worst place to spend attention.
Your third technique: the hidden single
A hidden single is a digit that can only go in one cell of a unit, even though that cell could also accept other digits.
Suppose a box has three empty cells and needs 2, 6 and 9. Two of those cells already have a 6 in their row or column; only the third can take it. The 6 goes there — regardless of what else that cell could have held.
Hidden singles solve the large majority of easy and medium Sudoku puzzles, and cross-hatching is simply the systematic way of finding them.
Should beginners use pencil marks?
Not at first, and this surprises people.
Pencil marks — writing every possible digit small in each empty cell — are a real tool, but they are the slowest one. Filling an easy grid with candidates costs about ninety seconds of writing before you place anything, and you will never use most of them.
Do two full cross-hatching passes with no marks at all. On an easy puzzle that usually finishes it. Only when placements dry up should you mark, and then only the single emptiest box or row — never the whole grid.
Reading the grid like a solver
Count what is missing, not what is there
Beginners read a row and see seven digits. Solvers read the same row and see two blanks and two missing digits — a two-second deduction instead of a nine-way comparison. Before scanning any unit, glance at how many cells are still empty. A row missing two digits is worth five seconds; a row missing seven is not worth looking at yet.
Look at three boxes at once
Because a digit appears only once per row, three horizontally adjacent boxes constrain each other tightly. Looking at the whole band rather than one box turns three separate searches into a single glance. This is the habit that makes experienced solvers look like they are placing digits without scanning.
Follow the digit you just wrote
Every placement changes exactly three units: its row, its column and its box. The next available placement is usually inside one of them. Checking those three before looking anywhere else is what produces the cascades that finish easy grids in a couple of minutes.
Choosing your first puzzles
Not every "easy" puzzle is genuinely a beginner puzzle, and starting on the wrong one is the most common reason people give up in week one.
| Source | Good for beginners? | Why |
|---|---|---|
| Newspaper Monday grid | Yes | Deliberately gentle; difficulty rises through the week |
| Puzzle books marked "easy" | Usually | Consistently rated, hand-checked by a publisher |
| Free mobile apps | Careful | Ratings vary wildly; some generate grids without checking uniqueness |
| Anything labelled "expert" or "evil" | No | Requires techniques you will not learn for months |
| 4×4 or 6×6 grids | Yes, for children | Same three rules, much smaller search |
If a grid gives you nothing after ten minutes of cross-hatching, it is probably not an easy grid. Change puzzle rather than concluding you cannot do Sudoku.
What to do when you get stuck
- Change digit. If the 4 is producing nothing, move to the next most frequent digit. Stalling on one digit is not the same as stalling on the grid.
- Change region. Move to the fullest box you have not scanned recently. Constraints concentrate where digits already are.
- Re-check the boxes. Beginners overwhelmingly forget the 3×3 constraint and check only rows and columns. Go back and verify by box.
- Do a second full pass. Everything you placed changed the grid. Cells that were ambiguous ten minutes ago may now be forced.
- Mark one unit. Only the emptiest box or row. Write every possible digit in each empty cell there and look for a cell with just one candidate.
- Take a break. Sudoku is a visual search task; tired eyes re-read the same regions without seeing them. Ten minutes away genuinely restores it.
Sudoku for children
The same three rules work at smaller sizes, and smaller grids are the right entry point for younger players.
- 4×4 — digits 1 to 4, four 2×2 boxes. Suitable from around age five. Teaches the three constraints without overwhelming the eye.
- 6×6 — digits 1 to 6, boxes of 2×3. A genuine step up, usually around age seven or eight.
- 9×9 easy — realistic from about age nine, once cross-hatching makes sense.
The teaching order is the same at every size: rules first, then cross-hatching one digit at a time, then following the consequences of each placement. Skip pencil marks entirely with children — they add bookkeeping without adding understanding.
Why Sudoku is worth learning
Beyond the puzzle itself, Sudoku has a few unusual properties. It needs no equipment, no opponent and no setup. It scales from five minutes on a phone to forty minutes in an armchair. And it is one of very few pastimes where you can watch your own competence improve on a measurable curve — your times drop, week by week, from something you can see yourself doing differently.
It also trains a genuinely transferable habit: never commit to an answer you cannot prove. That is worth something well outside a 9×9 grid.
The seven mistakes every beginner makes
- Guessing. A guess that seems to work collapses ten moves later, far from the mistake, and you cannot trace it. Every valid Sudoku is solvable without guessing.
- Forgetting the box. Beginners check rows and columns and overlook the 3×3 box — the constraint that makes Sudoku a puzzle rather than a simple grid.
- Starting in the emptiest area. Constraints concentrate where digits already are. Work the dense regions.
- Restarting the scan after every placement. Throws away the information the placement just created.
- Marking everything immediately. Ninety seconds spent on candidates you mostly will not need.
- Not erasing candidates. A stale pencil mark eventually causes a wrong placement.
- Giving up on hard grids too early. Long pauses are normal above medium level and are not a sign you are doing it wrong.
How long an easy grid should take
| Stage | Easy grid time | What you can do |
|---|---|---|
| First week | 15–25 min | Rules, cross-hatching one digit at a time |
| First month | 5–10 min | Naked and hidden singles, frequency order |
| Three months | 2–4 min | Chains, band reading, medium grids |
| Six months | 90 sec–2 min | Naked pairs, hard grids becoming possible |
A first-week practice plan
- Days 1–2. Easy grids only. No pencil marks, no timer. Practise cross-hatching a single digit through all nine boxes.
- Days 3–4. Add digit counting: always start with the most frequent digit.
- Days 5–6. After every placement, check that digit's row, column and box before looking anywhere else.
- Day 7. Solve three easy grids and note the times. Compare with day 1 — most people are twice as fast.
Two or three grids a day is plenty. Long sessions build fatigue rather than skill.
Where to go next
Once easy grids are comfortable, move to medium and add naked pairs — two cells in one unit holding exactly the same two candidates, which removes those digits from the rest of that unit. After that come pointing pairs and box-line reduction, which are what hard puzzles are built around.
The full ladder is in our guide to how to solve Sudoku step by step.
Frequently asked questions
What are the rules of Sudoku?
Fill the 9×9 grid so that every row, every column and every 3×3 box contains the digits 1 to 9 exactly once. There is no arithmetic, and a valid puzzle has exactly one solution reachable by logic.
How do you play Sudoku for beginners?
Pick one digit and find where it can go in each 3×3 box, rather than asking what fits in each empty cell. Start with the digit that already appears most often on the grid. That single habit is the whole beginner method.
Is Sudoku a maths puzzle?
No. There is no arithmetic in Sudoku at all. The digits are nine distinct symbols and could be replaced by letters or colours without changing the puzzle. It is a pure logic and pattern game.
What is cross-hatching?
You take one digit, find every existing copy of it, and cross out the rows and columns they occupy. Any box that needs the digit and has only one free cell left is solved instantly. It is the foundation of every other technique.
What is the difference between a naked single and a hidden single?
A naked single is a cell where only one digit can possibly fit. A hidden single is a digit that can only go in one cell of a unit, even if that cell could accept other digits too.
Should beginners use pencil marks?
Not at first. Marking every cell costs about ninety seconds before you place anything, and easy grids rarely need it. Do two full cross-hatching passes first, then mark only the emptiest box or row.
Do you ever have to guess in Sudoku?
No. A properly constructed puzzle has exactly one solution reachable by logic alone. If you feel forced to guess, an elimination has been missed somewhere on the grid.
Where should I start on a Sudoku grid?
In the fullest region, not the emptiest. Constraints concentrate where digits already sit, so a row with seven digits placed or a box with six is where forced placements hide.
How long should an easy Sudoku take a beginner?
Fifteen to twenty-five minutes in the first week, five to ten minutes after a month, and two to four minutes after three months of regular practice.
How many clues does a Sudoku have?
Typically 22 to 30. The proven minimum for a unique solution is 17, established in 2012 by exhaustive computer search. Clue count and difficulty are only loosely related.
Can a Sudoku have more than one solution?
A properly constructed one cannot. If you reach a point where two digits are freely interchangeable with no elimination available, the puzzle is faulty — which does happen in free apps that generate grids without checking uniqueness.
What should I learn after the basics?
Naked pairs first, then pointing pairs and box-line reduction. Those three cover almost everything up to hard level. X-Wing and beyond are only needed on expert grids.
How do I check my Sudoku is correct?
Every row, every column and every 3×3 box must contain the digits 1 to 9 exactly once, with no repeats. To verify instantly, enter the puzzle into our free Sudoku solver and compare.
Play your first grid
Find an easy puzzle, count the digits, and cross-hatch the most frequent one through all nine boxes before writing anything else. That is the whole beginner method, and it will carry you through every easy grid you meet. When one stops you, our free online Sudoku solver gives you the complete answer in a second.
Next, read: How to Solve Sudoku — The Complete Guide · Sudoku Tips and Tricks · Solve a Sudoku in 1 Minute
