You see Sudoku grids everywhere (in the paper, in waiting rooms, on your phone), but you have never dared to try? You are in the right place.
Good news straight away: Sudoku requires no mathematical knowledge whatsoever. You never add or multiply anything. The digits are merely symbols: you could play with nine colours or nine letters and it would be exactly the same game.
What a grid is and how to read it, the goal of the game, the rules (there is really only one, stated three ways), the first reflex to get started, and a practice grid with its solution.
🎬 The introduction video
This very accessible video covers the three essentials: what Sudoku is, the goal of the game and the rules, all illustrated with examples. The practice grid offered at the end of the video appears further down this article.
▶ English audio track and English subtitles: pick either from the ⚙️ icon.
Found this video helpful? Over 120 free Sudoku tutorials are waiting on the channel, from beginner to expert level.
▶ Subscribe for free1
What is a Sudoku grid?
A Sudoku grid is a square of 81 cells, arranged in 9 rows and 9 columns. That square is itself divided into 9 boxes of 3×3 cells, marked out by thicker lines.
These three divisions (rows, columns and boxes) are called units. Each contains exactly 9 cells, and the whole game rests on them.
Rows are labelled R1 to R9 (top to bottom) and columns C1 to C9 (left to right). The top-left cell is therefore R1C1. This notation is very handy as soon as you want to describe a deduction.
At the start, some cells already contain a digit: these are the givens. They never change. All the other cells are empty and it is up to you to fill them. The more givens there are, the easier the grid.
2
The goal of the game
Fill every empty cell with digits from 1 to 9, without ever breaking the rules.
That is all. There is no score, no opponent, no compulsory timer. A properly constructed grid has a single solution, and that solution can always be found by reasoning, never by luck.
This matters for a beginner: if you are reduced to guessing, a deduction has escaped you. Somewhere in the grid there is always a cell whose content is certain.
3
The rules
In truth, Sudoku has only one rule, simply stated three ways:
- Each digit from 1 to 9 appears once per row
- Each digit from 1 to 9 appears once per column
- Each digit from 1 to 9 appears once per 3×3 box
In other words: in each of the grid's 27 units (9 rows + 9 columns + 9 boxes), every one of the nine digits appears exactly once.
Many people diligently check the row and the column… and forget the box. It is the number one source of error when starting out. Get into the habit of checking all three before placing a digit.
Bonus
Your first reflexes
The rules do not say how to find the digits. Here is the simplest method, more than enough for easy grids: scanning.
Step 1, Pick a digit
The 1, for instance. Spot every cell where it is already placed in the grid.
Step 2, Eliminate visually
Each 1 already placed “forbids” its entire row, its entire column and its entire box. Take a box where the 1 is still missing, and mentally cross out the rows and columns already occupied by a 1.
Step 3, Is only one cell left?
If a single cell in that box survives the elimination, that is necessarily where the 1 goes. Place it, then start again with the next digit.
Repeat for all nine digits, several times over: each digit placed frees up others. On an easy grid, this single reflex is often enough to solve everything.
When scanning stops producing results, it is time to mark the candidates in the cells, then learn your first techniques, starting with hidden pairs.
🧩 Practice grid
Here is the grid offered at the end of the video. It is beginner level and can be solved entirely by scanning: take your time, check each digit against all three units, and never guess.
Practice grid, beginner level
Tap a cell then a digit. On keyboard: 1-9, arrows, Delete.
🎬 Stuck? Revisit the method
The video does not give the solution to this grid: it explains the beginner reflexes, then offers the grid as practice. If you get stuck, that is where to go back.
❓ Frequently asked questions
No, not at all. Sudoku requires no arithmetic: you never add or multiply anything. The digits 1 to 9 are just symbols, and nine colours or nine letters would work equally well. It is a game of pure logic and observation.
Yes, a properly constructed grid admits only one possible solution, and that solution can always be reached by reasoning. If you find yourself having to guess, either a deduction has escaped you or the grid is badly built.
Expect 5 to 15 minutes for a beginner-level grid when starting out, dropping quickly to a few minutes with practice. Speed does not matter at the beginning: focus on understanding each deduction first.
With scanning: pick a digit, spot where it is already placed, and look for the box where only one cell remains possible for it. It is the simplest technique and it is enough to fully solve easy grids.
📋 Summary
Sudoku in five points
- 81 cells : 9 rows, 9 columns, 9 boxes of 3×3
- The goal : fill every empty cell with digits 1 to 9
- The rule : each digit once per row, per column and per box
- No arithmetic : the digits are plain symbols
- Never luck : one single solution, always reachable by deduction
You now know everything you need to start. What follows is practice: run through a few easy grids until scanning becomes automatic, then move on to your first techniques.
📘 Going further
Once the basics are in place, the Domino33 memento takes you all the way: 40 techniques explained sheet by sheet, from beginner to expert.
