You know the rules (if not, How to Play Sudoku takes a minute). These are the habits that separate a puzzle you finish from one you abandon halfway through.
1. Start with the most common digit
Count which digit appears most often among the givens. It has the fewest places left to go, so it’s the easiest to place. Finish it, then move to the next most common.
2. Scan by digit, not by cell
Beginners tend to stare at an empty cell and wonder what goes there. It’s usually quicker to pick a digit and ask where it goes in each box. That’s how you find Hidden Singles, which carry most Easy and Medium puzzles.
3. Work on the crowded areas
A row, column or box with seven or eight digits filled in has only one or two gaps. Those gaps are nearly solved already.
4. Use all three houses
Every time you check a cell, check its row, its column and its box. Forgetting the box is the most common reason a “certain” digit turns out to be wrong.
5. Never guess
A proper sudoku can always be solved by logic. If you guess and you’re wrong, you may not find out for twenty moves, by which time the grid is in a mess. If you’re stuck, there is something you haven’t seen yet. Look again.
6. Bring in notes when scanning dries up
Easy puzzles rarely need notes. From Medium onwards, pencil in candidates for the cells you’re working on. Once a puzzle reaches Hard, fill them in everywhere: the next techniques work on candidates, not on placed digits.
7. Keep your notes honest
When you place a digit, remove it from the notes of every peer. Out-of-date notes are worse than none. (One Sudoku does this automatically when you place a digit.)
8. Look for pairs
When two cells in the same house have the same two candidates and nothing else, those two digits are taken. Clear them from the rest of the house. That’s a Naked Pair, and it’s the first technique that unlocks Hard puzzles.
9. Take a break when you’re stuck
Coming back after five minutes works surprisingly often. You’ll see the grid fresh and spot the move you kept looking past.
10. Play one level above comfortable
If you never get stuck, you aren’t learning anything new. If you’re stuck on every move, drop back down a level. A couple of hard moments per puzzle is the sweet spot.
A rough timeline
| If you can… | You’re ready for… |
|---|---|
| Finish Easy in about 5 minutes | Medium |
| Finish Medium in about 10 minutes | Hard, with pairs and pointing |
| Finish Hard in about 15 minutes | Expert, with the X-Wing |
These are the target times One Sudoku uses for its star rating. Learn Sudoku: A Clear Path from Easy to Expert lists exactly which techniques each level asks for.
