Staring at a blank Sudoku grid for the first time can feel a little overwhelming. Nine rows, nine columns, eighty-one boxes, and a handful of numbers scattered across the page — where on earth do you begin? The good news is that every Sudoku puzzle, no matter how difficult it looks, has a logical starting point. You just need to know where to look. This guide will walk you through the best way to start a Sudoku puzzle as a beginner, giving you a clear, step-by-step approach that will have you filling in numbers with confidence right from your very first solve.
Understanding the Basic Rules Before You Begin
Before you place a single number, it helps to make sure the rules are crystal clear. Sudoku is a logic-based number puzzle played on a 9×9 grid. That grid is divided into nine smaller 3×3 sections called boxes (sometimes called regions or blocks). The puzzle already has some numbers filled in — these are called givens or clues — and your job is to fill in the rest.
The three golden rules of Sudoku are:
- Every row must contain the numbers 1 through 9, with no repeats.
- Every column must contain the numbers 1 through 9, with no repeats.
- Every 3×3 box must contain the numbers 1 through 9, with no repeats.
That’s it. There are no tricks beyond these three rules. Every solving technique you will ever learn is simply a method for using these rules cleverly to figure out which number belongs in which empty cell. Keep these rules in front of you as you work through your first few puzzles, and refer back to them whenever you feel stuck.
Step One: Scan the Grid Before Writing Anything
The single best habit a beginner can develop is to scan the entire grid before placing any number. This sounds simple, but many beginners dive straight in and start guessing, which leads to mistakes and frustration. Take sixty seconds at the start of every puzzle to look at the big picture.
Here is what to look for during your initial scan:
- Which numbers appear most often? If you can count five or six instances of the number 7 already placed on the grid, it will be much easier to figure out where the remaining 7s belong, because most rows, columns, and boxes already have them.
- Which rows, columns, or boxes are nearly complete? A row that already has eight numbers filled in only needs one more — you can solve it instantly by identifying the missing digit.
- Which 3×3 boxes look the fullest? Boxes with more clues are easier to work with first, because you have more information to reason from.
This scanning step is the foundation of a technique called cross-hatching, which is the most beginner-friendly solving method in Sudoku. We will cover it in detail next.
Step Two: Use Cross-Hatching to Find Easy Numbers
Cross-hatching is the technique of eliminating possibilities by looking at the rows and columns that pass through a particular 3×3 box. It sounds technical, but the idea is beautifully simple: if a number already exists in a row or column that crosses through a box, that number cannot appear again in that row or column — which means you can rule it out of certain cells inside the box.
Let’s work through a concrete example. Imagine you are looking at the top-right 3×3 box of the puzzle, and it is currently empty. You want to figure out where the number 3 goes. You look at the three rows that run through that box (rows 1, 2, and 3) and discover that row 2 already has a 3 in it somewhere on the left side of the grid. That means row 2 inside your top-right box cannot contain another 3. Next, you look at the three columns that pass through the box (columns 7, 8, and 9) and find that column 9 already has a 3 in another box. Now you know that column 9 cannot hold the 3 either. If the intersection of row 2 and column 9 is already eliminated, and a third cell is already filled with a different number, you might find that only one cell in the entire box is still available for the number 3. When that happens, you have solved that cell — no guessing required.
Work through each number from 1 to 9 and apply cross-hatching to every box. You will often find several cells that can be solved immediately just with this one technique. For an easy or medium Sudoku puzzle, cross-hatching alone can sometimes take you most of the way to a complete solution.
Step Three: Use the “Last Remaining Cell” Technique
Once you have done a round of cross-hatching, look for rows, columns, and boxes that are almost complete. The last remaining cell technique is exactly what it sounds like: if a row, column, or box has eight numbers already placed, the ninth number is simply whichever digit from 1 to 9 is missing.
For example, suppose row 5 contains the numbers 1, 2, 3, 4, 6, 7, 8, and 9, with only one blank cell remaining. By process of elimination, that blank cell must contain 5. You do not need to check anything else — it is the only number that can legally go there.
This technique also works for groups that are not quite at eight numbers. If a column has seven numbers filled in, you have two missing digits to work out. Identify what those two numbers are, and then use cross-hatching or other clues to decide which one goes where. Breaking the problem into small, manageable steps like this keeps the puzzle feeling approachable rather than overwhelming.
Step Four: Write Pencil Marks for Harder Cells
After your first pass through the grid using cross-hatching and the last remaining cell technique, you will likely hit cells where you cannot immediately determine the answer. This is completely normal, even for experienced solvers. The next tool in your beginner’s toolkit is pencil marks (also called candidates or possibility notes).
Pencil marks are small numbers written lightly inside a cell to record which digits are still possible for that cell. For example, if a cell could legally contain either a 4 or a 7 — and nothing else — you would write a tiny “4” and “7” inside it. As you solve other cells around it, you can erase pencil marks that are no longer valid.
Here are some tips for using pencil marks effectively:
- Write them small and neatly so the grid does not become cluttered and hard to read.
- If you are solving digitally on a site like playsudoku.org, use the built-in notes function to keep track of candidates without cluttering your view.
- After placing any confirmed number, go through the related row, column, and box and delete that number from all pencil marks immediately. This keeps your notes accurate and often reveals new solutions.
- Look for cells where only one candidate remains — these can be filled in straight away. This is called a naked single, and it is one of the most satisfying moments in Sudoku.
Pencil marks transform a puzzle from a guessing game into a structured logical exercise. Many beginners resist using them because they feel like extra work, but they actually save time and dramatically reduce errors in the long run.
Common Beginner Mistakes to Avoid
Knowing what not to do is just as valuable as knowing what to do. Here are the most common mistakes beginners make when starting a Sudoku puzzle:
- Guessing too early. Sudoku is a logic puzzle, not a lottery. If you find yourself guessing without any reasoning behind your choice, step back and scan the grid again. There is almost always a logical deduction you have missed.
- Focusing on only one area. Beginners often fixate on one corner of the grid and try to complete it entirely before moving on. A better approach is to scan the whole grid repeatedly, picking up easy wins wherever they appear.
- Forgetting to update pencil marks. Placing a new number without erasing that number from the pencil marks in its row, column, and box is a common source of errors. Make updating your notes a habit every time you fill in a cell.
- Rushing. Sudoku rewards patience. Slow down, double-check your reasoning, and enjoy the process of logical deduction. Speed comes naturally with practice.
Building Confidence: Start With Easy Puzzles
Every expert Sudoku solver started exactly where you are right now. The key to building genuine confidence is to begin with puzzles that are rated easy and work your way up gradually. Easy puzzles are designed to be solvable using only the most basic techniques — cross-hatching, last remaining cell, and naked singles — which makes them perfect for practising the starting strategies described in this article.
Once you can consistently solve easy puzzles without making errors, try medium-difficulty puzzles. You will find that the starting approach stays exactly the same — scan, cross-hatch, use last remaining cells, write pencil marks — but you will need to push a little deeper into your logic to crack the trickier cells. From there, the natural progression leads to techniques like hidden singles, naked pairs, and eventually more advanced strategies like pointing pairs and box-line reduction. But all of that comes later. For now, mastering your starting routine is the most important thing you can do.
Key Takeaways
Starting a Sudoku puzzle well sets the tone for the entire solve. Here is a quick summary of everything covered in this guide:
- Always understand the three rules fully before you begin: no repeated numbers in any row, column, or 3×3 box.
- Scan the whole grid first to identify which numbers appear most frequently and which rows, columns, or boxes are nearly complete.
- Apply cross-hatching by looking at rows and columns that pass through each box to eliminate candidates and find confirmed numbers.
- Use the last remaining cell technique to quickly solve rows, columns, and boxes that have only one or two cells left.
- Write pencil marks for cells where you cannot immediately determine the answer, and update them every time you place a new number.
- Avoid guessing, stay patient, and start with easy puzzles to build solid habits before progressing to harder difficulties.
Learning to start a Sudoku puzzle the right way is one of the most rewarding steps in the solving journey. Once this routine clicks into place, you will find that puzzles which once looked impossibly complicated begin to reveal their secrets one satisfying step at a time. Head over to playsudoku.org, pick an easy puzzle, and give these techniques a try — your first successful solve is closer than you think. Good luck, and enjoy the puzzle!