How to Solve Sudoku: Rules, Steps, and Practice
Solving Sudoku becomes easier when you use one steady routine: confirm the rules, scan for singles, write candidates only when needed, and practice on a puzzle that matches your current level. This page works as the main roadmap: learn the basics, choose the right guide, then move directly into a playable puzzle.
Start with the three constraints
Every row, column, and 3x3 box must contain 1 through 9 without repetition. Before looking for advanced patterns, check which numbers are already blocked by these three constraints. A number is safe only when all three checks agree.
Choose the easiest area first
Do not scan the board randomly. Start with rows, columns, or boxes that already contain many given numbers. These areas have fewer missing digits and often reveal the first safe placement.
Place obvious singles
An obvious single is a cell where only one digit remains possible after checking the row, column, and box. These placements build momentum and reduce the number of open cells.
Look for hidden singles
A hidden single appears when a digit has only one possible position inside a row, column, or box. The cell may have several apparent candidates, but the unit gives the answer.
Use candidates when progress slows
When no single is visible, write candidates in the area that is stuck. Candidate notes should help you compare options and remove impossible digits, not fill the whole board with noise too early.
Eliminate before you guess
Guessing makes it hard to learn from the puzzle. Instead, ask why each candidate can or cannot stay. Remove numbers using row, column, box, and simple pair logic before making a placement.
Review contradictions calmly
If the puzzle breaks, return to the last uncertain move and check the three rules again. Most beginner contradictions come from missing a row, column, or box duplicate.
Pick the right practice mode
Use Beginner when you are learning the routine, Daily when you want a repeatable habit, and Intermediate when candidates feel natural. The best level is the one where you can explain most moves without guessing.
Practice immediately after reading
The fastest way to retain a Sudoku technique is to use it on a real board. Read one guide, apply one idea, then review where the puzzle slowed down before starting another board.
Related learning links
Review rows, columns, boxes, and the no-duplicate rule.
Read guide →Beginner step-by-step guideFollow a repeatable routine for easy Sudoku puzzles.
Read guide →Candidate elimination guideLearn how to remove impossible numbers without guessing.
Read guide →Beginner mistakesAvoid the habits that create contradictions and stalls.
Read guide →Practice now
FAQ
Look for rows, columns, or boxes that already contain many numbers, because they usually reveal the safest singles.
No. Guessing hides the reason a move works. Use candidates and elimination so every placement has a clear logic trail.
Use candidates when obvious singles and hidden singles stop appearing. Start in the stuck area instead of marking every empty cell immediately.
Start with Beginner if you are learning the rules or building a solving routine. Add Daily and Intermediate puzzles once easy boards feel stable.