The everyday puzzle
Medium is where most people settle. There are about thirty starting numbers, scanning carries you through the opening, and then the grid asks for something more — usually pointing pairs, the move where a digit trapped on one line inside a box can be struck out of the rest of that line.
When to start writing pencil marks
Not straight away. Filling all eighty-one cells with candidates before making a single placement is slow and error-prone. The better habit is to scan until nothing new appears, then mark up only the box or line that looks most constrained.
The notes button on the board does this bookkeeping properly: enter a digit and it is removed from the pencil marks of every cell that can see it.
Getting faster
- Count how many of each digit are already placed — the ones with seven or eight copies on the board are nearly always the next placement.
- Look at bands of three boxes rather than single boxes; that is where hidden singles hide.
- Before you write a candidate list, check the row, the column and the box. Half of the lists you were about to write turn out to have one entry.
- Use the hint button when you are stuck. It names the technique and shows you where it applies, which is how you learn to see it unaided.
Coming from easy? The step up is one technique, not ten. Ready for the next one? Hard brings in pairs and triples.
Common questions
How many clues does a medium Sudoku have?
Usually 30 to 35. The exact number matters less than the moves required — every medium puzzle here needs at least one candidate technique beyond plain scanning.
How long does a medium puzzle take?
Typically 8 to 15 minutes. Under five is quick.
Do I need pencil marks for medium?
Usually for part of the grid, rarely for all of it. Mark up the most constrained unit rather than the whole board.
What is the difference between medium and hard?
Medium needs at most a locked-candidate move. Hard adds naked pairs, hidden pairs and triples, and gives you a few clues less to work with.