How to Solve Sudoku Faster — Speed Tips for Every Level

Most people solve Sudoku by staring at a cell and trying every number until something fits. That works — eventually. But it's the slowest possible method. Here are five techniques that will make you noticeably faster, immediately.

1. Scan by number, not by cell

Instead of picking a cell and asking "what number goes here?", pick a number and ask "where in this box can this number go?" Find all existing instances of, say, 7. Their rows and columns eliminate most candidates. The remaining box cells are your targets.

2. Start with the most constrained groups

Scan all 27 groups (9 rows, 9 columns, 9 boxes). The group with 7 or 8 givens is nearly solved — it takes seconds. The group with 3 givens needs other cells filled first. Always work from most-filled to least-filled.

3. Use pencil marks — even though it feels slower

Writing small candidate numbers seems slower than thinking. It isn't. Mental tracking fails the moment you're interrupted or make a mistake. Pencil marks are permanent. The time spent writing is recovered immediately when you spot patterns you'd have missed.

4. Last Remaining Cell (LRC)

If 8 of 9 cells in a group are filled, the 9th gets the missing number. Obvious — but most people don't check for LRC automatically after every placement. Make it a habit. After placing any number, scan its row, column, and box for LRC opportunities.

5. Exploit chain reactions

Every placement constrains its row AND its column simultaneously. After placing a number, immediately ask: does this now make another placement obvious in an adjacent box? Chain placements — 3 or 4 in a row — are how fast solvers build momentum.

The single biggest time-waster

Returning to cells you already analysed and getting the same result. Use pencil marks so you don't repeat work. When a cell is genuinely stuck, mark it and move on — other placements will eliminate its candidates.