The everyday puzzle
Medium is where most people settle. There are about thirty-three starting numbers, scanning carries you through the opening, and then the grid usually asks you to change how you look: instead of asking which digit fits a cell, ask where a digit can go in a row, column or box. That is a hidden single, and about half the medium grids here need at least one.
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 way of looking, not ten new techniques. Ready for the next one? Hard leans on hidden singles throughout, and some grids need locked candidates.
What these puzzles actually need
We generated 300 puzzles at this level with the same code that builds the board above, solved each one along its logical path, and counted. A technique counts if the path uses it at least once.
| Measured across the sample | Medium |
|---|---|
| Starting numbers, fewest to most | 32–39 |
| Starting numbers, average | 33.3 |
| Moves to solve, average | 48 |
| Solved by naked singles alone | 55% |
| Need a hidden single | 45% |
| Need locked candidates | 1% |
| Need a naked or hidden pair or triple | 0% |
| Need an X-Wing, XY-Wing or Swordfish | 0% |
The sample uses fixed seeds and is measured again whenever the generator changes, so these figures describe the puzzles this page actually serves.
Common questions
How many clues does a medium Sudoku have?
Usually 32 to 35. The exact number matters less than the moves required — medium grids have a longer solving path than easy ones, and about half of them need a hidden single somewhere.
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?
Hard grids start with about five clues fewer, every one of them needs hidden singles, and roughly one in five needs a locked-candidate move. Medium grids almost never do.