Sudoku Unlocked
Welcome to Sudoku
You are staring at a grid full of numbers and empty squares. There are no sums to solve and no equations to remember. Everything you need is already sitting in front of you. Your job is to examine the clues, eliminate the impossible, and discover where every number belongs.
Welcome to Sudoku: a puzzle where you think like a detective!
What Is Sudoku?
Sudoku is a number puzzle, but it is not really a maths test. You do not need to add, subtract, multiply, or divide. Instead, you use logic to work out where each number belongs. A standard puzzle has 81 squares arranged into:
- 9️⃣ Rowsnine horizontal lines across the puzzle
- 9️⃣ Columnsnine vertical lines down the puzzle
- Nine BoxesThe grid has nine smaller 3 x 3 boxes!
- Each row, column, and box has numbers 1 to 9 once!
The Mission
Some numbers are already filled in. These are your clues. Your job is to use those clues to complete every empty square. When you finish, every row, column, and 3 × 3 box should contain 1 to 9 exactly once.
The Three Golden Rules
Sudoku becomes much easier when you remember three rules.
Check the row. Check the column. Check the box. If a number breaks any one of these rules, it cannot go there.
- 1️⃣ Check the RowEvery row must have numbers 1 to 9, each used only one time. No repeats in a row!
- 2️⃣ Check the ColumnEvery column must have numbers 1 to 9, each used only one time. No repeats, wow!
- 3️⃣ Check the Boxevery 3 × 3 box must contain the numbers 1 to 9 once. No number can appear twice in the same box
How to Find Your First Number
You do not need to solve the whole puzzle at once. Start by looking for the easiest clues.
- A row with one missing number1 2 3 4 5 6 _ 8 9. The answer is 7!
- An almost full columnif only one number is missing, it must be 6
- An almost full boxeight numbers and one empty square. The missing number is your next clue
The Detective Method
Sudoku is really a giant process of elimination. Imagine you are investigating the question: where can the number 5 go?
Find the clues. Eliminate the impossible. Find the only possibility. Check your answer.
- Find the CluesLook for where the number 5 already appears in the puzzle!
- Eliminate Impossible SquaresIf a square shares a spot with a 5, no 5 here!
- Find the PossibilityIf only one square is left, you solved the puzzle!
- Check Your WorkMake sure your answer follows all three golden rules!
Pencil Marks
Sometimes you will not know the answer immediately. That is completely normal. You can write tiny possible numbers inside an empty square, like 2 or 7. Later, another clue might show that 2 cannot fit. Then only 7 remains!
A possibility is not an answer. Pencil marks are clues, not confirmed numbers. Do not commit until you have enough evidence.
Sudoku Detective Techniques
Once you understand the basics, you can start using more powerful techniques.
Sudoku gets interesting when one clue unlocks another!
- 1️⃣ Single Missing NumberOnly one number is missing from a row, column, or box. Super easy!
- 2️⃣ ScanningPick a number! Follow it through the puzzle. Each existing 7 blocks certain spaces
- 3️⃣ Naked SingleIf just one number can fit in a square, you've found its perfect spot!
- 4️⃣ Hidden SingleA number that only fits in one square in a row, column, or box is home!
- 5️⃣ Pairstwo squares with the same two possibilities mean other squares in that unit cannot use those numbers
The Sudoku Chain Reaction
One answer can create another answer, and that answer can create another. You solve 7, so another square cannot be 7, so only 3 can fit there, and that new 3 blocks another square. A new answer appears!
One clue can unlock the next clue. That is why Sudoku can feel like solving a mystery.
Common Sudoku Mistakes
Even experienced players can make mistakes.
If you have to guess, stop and search for another clue.
- GuessingIt can send you the wrong way! Look for another clue first.
- Checking Only RowA number might fit but break column or box rule!
- Forgetting the BoxThe 3 × 3 box is just as important as rows and columns!
- Trusting Pencil MarksA possible number is not a confirmed answer yet!
- Repeating a NumberEach row, column, and box holds numbers just one time!
- Ignoring a MistakeIf the puzzle gets stuck, check your previous moves!
Easy, Medium and Hard Sudoku
Not every puzzle is difficult for the same reason, and difficulty is not simply about how many empty squares there are.
More empty squares does not automatically mean a harder puzzle. The real question is how much logical thinking it requires.
- Easylots of clues and many single missing numbers! Great for learning!
- Mediumscanning, pencil marks, and hidden singles. Clues work together!
- Hardclues connect across different parts of the grid. You think several steps ahead
Does Sudoku Make You Smarter?
Sudoku is not a magic intelligence machine, but it can give your brain useful practice.
You do not have to solve everything at once. Solve one small problem, then use that answer to solve the next one.
- ConcentrationYou focus on clues to solve the puzzle!
- Logical ThinkingUse rules to nix impossible answers!
- Pattern RecognitionSee numbers + how they fit!
- PatienceSome fun puzzles take a little time!
- Checking Your WorkYou learn to look back and test your choices!
- Problem SolvingA big puzzle splits into smaller, easier problems.
Training Grids
Before tackling a full 9 × 9 Sudoku, you can practise with smaller grids. The same detective rules still apply.
- 4 × 4 Sudokuuses numbers 1 to 4 and little 2 × 2 squares!
- 6 × 6 Sudokuuses numbers 1 to 6 and little 2 × 3 boxes!
- 9 × 9 Sudokuthe classic grid. Nine rows, nine columns, nine boxes, numbers 1 to 9
Spot the Mistake!
A Sudoku detective must also catch errors. Imagine you see 1 2 3 4 5 6 7 8 7. Something is wrong! The number 7 appears twice. Check the row, check the columns, check the box, and find where the mistake began.
Do not simply fix the last number you wrote. Find the clue that caused the mistake.
The Sudoku Thinking System
Before writing a number, try this routine. Then start again.
LOOK. CHECK. ELIMINATE. SOLVE.
- LOOKWhat numbers are around this box?
- ROWWhich numbers are in this whole row?
- COLUMNwhich numbers already appear in the column?
- BOXwhich numbers already appear in the 3 × 3 box?
- ELIMINATEcross out impossible numbers
- FINDis there only one possibility left?
- CHECKDoes your answer follow rules?
- WRITEOnly then put the number down!
Sudoku Around the World
Sudoku is one of the world's best known logic puzzles. You can find it in newspapers, puzzle books, websites, apps, classrooms, and competitions where players race to solve puzzles accurately.
- Schoolsa logic and problem solving activity
- Newspapersa popular puzzle around the world
- Appsdigital Sudoku can check moves, give hints, and make puzzles!
- Competitionsplayers race to solve puzzles quickly and correctly!
Sudoku and Computers
Computers can solve Sudoku extremely quickly by testing possible numbers far faster than a human. But solving it yourself gives you something different: the experience of discovering the logic step by step.
The computer can find the answer. The fun is understanding how you found it.
Amazing Sudoku Facts
81 Squares
A standard grid has 81 squares: 9 rows x 9 columns.
9 Boxes
The grid has nine smaller 3 x 3 boxes inside it.
No Math Skills Here!
No sums! You never add, subtract, multiply, or divide.
Domino Effect Fun!
One solved square can open many others, like a chain!
Logic Only Sudoku!
Good Sudokus use pure logic. No guessing needed, just smart thinking!
Be Right, Not Fast!
Rushing a wrong answer isn't solving! Be smart, be right, be quick!
Summary
🔢 Numbers
Use numbers 1 to 9 only!
📏 Rows
Each row needs every num!
⬇️ Columns
Each column needs every number once
📦 Boxes
Each 3 × 3 box needs every number once
No Way Out!
Remove bad answer choices!
Think Smart
Use clues! Don't just guess!
Ready for the challenge?
Sudoku Detective Mission
You are a Sudoku detective solving a big puzzle championship. Use clues and logic, never guesses, to crack every grid.
Sudoku Dictionary
Grid
All the squares that form the puzzle, together!
Row
A line of squares that goes across the grid!
Column
It's a straight line of squares, up and down!
Box
It's one of nine big 3 by 3 areas in Sudoku!
Cell
It's one little square on the puzzle grid!
Clue
A number in the puzzle to help you solve!
Candidate
A number that might fit in an empty box. Wow!
Pencil Mark
A small note showing numbers for an empty box.
Naked Single
This cell has only one number that can fit!
Hidden Single
This number fits in only one cell in a group!
Search!
Look across rows, columns, and boxes to find a number's perfect spot to fit!
Twosie
Two cells have same two choices. Remove those choices from other cells now!
Elimination
Removing numbers that cannot legally fit in a cell
Solution
The completed grid where every rule is satisfied
Deduction
Working out what must be true from the information you already have
You Are Now a Sudoku Expert!
Great Sudoku players do not guess. They collect clues, eliminate impossible choices, spot patterns, and build one answer from another. Find the clue. Eliminate the impossible. Solve the puzzle.
