Sudoku
Most of the grid is already filled. Finish the marked cells as fast as you can, and see what the clock says.
This round measures how you work through row, column and box constraints right now.
Most of the board is already filled. Finish the 10 marked cells, as fast as you can.
- Tap an empty cell — its row, column and box light up
- Press a digit below to put it in
- A correct digit locks, and the count goes down
How to read your score
| Score | What it means |
|---|---|
| Under 45 seconds (Starter) | A net time under 45 seconds on the Starter tier of this Sudoku — ten cells to fill — is the fastest of five descriptive bands, not a ranking against other players. Ten cells at this pace usually means reading whole rows, columns and boxes rather than single cells. Compare it with your own Starter rounds on the same device. |
| 45-69 seconds (Starter) | A net time of 45 to 69 seconds on the Starter tier of this Sudoku is the second of five descriptive bands, and it is comfortably inside the 75-second Starter target. It is the pace of a clean pass: you found each forced cell without much backtracking. Net time includes ten seconds per wrong digit, so check the wrong-digit count beside it. |
| 70-109 seconds (Starter) | A net time of 70 to 109 seconds on the Starter tier of this Sudoku is the middle of five bands, not the middle of a population. The Starter target time is 75 seconds, so this band straddles it: two hint-free rounds at or under 75 seconds move you up to Steady. A few cells took a second look, which is what most rounds look like. |
| 110-179 seconds (Starter) | A net time of 110 to 179 seconds on the Starter tier of this Sudoku is the fourth of five bands and usually means scanning cell by cell instead of unit by unit. Ask which row, column or box is nearly full before picking a cell. A hint will name one such unit without giving you the digit. |
| 180 seconds or more (Starter) | A net time of 180 seconds or more on the Starter tier of this Sudoku is the slowest of five bands and a completely ordinary result for the first few rounds. It says nothing about ability. Play a few more and compare the times with each other rather than with this table. |
These ranges describe Starter rounds only; the other three difficulties have no reference range on this site yet, and a round there shows your own history instead. They come from internal test runs, not from a survey of players, so they cannot tell you how you compare with other people. Lower is better, and the fairest comparison is your own earlier rounds at the same difficulty.
How to play
- How do you start a round of timed sudoku?: Pick a difficulty, then press Start. Your first visit runs a three-cell warm-up that is not timed. After it, press the button to begin the scored round: a panel covers the board for 1.5 seconds, and the clock starts the moment it lifts.
- How do you place a digit in this sudoku?: Tap an empty cell to select it — its row, column and box light up — then press a digit on the keypad below. A correct digit locks into the cell and the remaining count drops by one. A wrong digit never enters the cell, so the board you are looking at is always correct.
- How do you use notes and hints in sudoku?: Turn on Notes and press digits to pencil candidates into the selected cell; notes cost nothing but the time you spend on them. A hint points at one cell you can already solve and names the row, column or box that proves it, never the digit. You can take as many hints as you like, but a round with a hint does not count toward your best time.
- How do you read your sudoku time here?: Your score is net time, and lower is better: the clock from the moment the panel lifts to the last correct digit, plus ten seconds for each wrong digit. Check actual time, wrong digits and hints beside it, then compare with your own earlier rounds at the same difficulty — that is the only fair comparison this page can offer.
What this measures
Each row, each column and each three-by-three box holds the digits 1 to 9 once each. Only the marked cells are yours to fill; the rest came with the puzzle.
There are four difficulties, and they differ by how many cells you fill: Starter 10, Steady 14, Sharp 18, Expert 24. The difficulty name is also the hardest technique a puzzle may need, and an easier puzzle can still appear in that tier.
The difficulty moves with you. Each tier has a target time — 75 seconds on Starter, 120 on Steady, 190 on Sharp, 300 on Expert, all net and all without hints. Finish two rounds in a row at or under the target and the next round steps up; go over it once and the next round steps back down. You can also pick a difficulty by hand at any time, and the ladder carries on from there.
Every puzzle has exactly one solution and is solvable without guessing. Each one is checked by a solver before it ships, and in a scored round no two empty cells ever sit side by side, so a mis-tap lands on a filled cell rather than on another answer.
Net time is the score: net time equals your actual time plus ten seconds for each wrong digit. Ten seconds is about what a careless guess would save you, which is what stops guessing from paying.
Tapping a cell costs nothing. Change your mind as often as you like; the only control that can produce an error is the digit keypad. Tapping a cell that is already filled clears your selection instead, so the next digit you press cannot drop into a cell you stopped looking at.
If two digits arrive almost on top of each other — a double tap, or a key you held down — the second one is thrown away instead of counted, so a slip of the finger can neither fill a cell for you nor cost you ten seconds.
A round ends without a time if you make six wrong digits in one cell, spend three minutes on a single cell, or take more than ten minutes overall. The same happens if you switch away, refresh or stop part-way. Times you already finished are untouched.
Times at different difficulties are kept apart, and so are best times: a Starter round and an Expert round are two different measurements wearing one label. The page always says which difficulty a best time belongs to.
The practice board is a whole 81-cell grid with no time limit and no record: its clock only tells you how long a board took, and never becomes a score. It pauses, it survives a refresh, it has an undo button, and it is where to go if you want to take your time.
FAQ
What are the rules of sudoku?
Fill the grid so that every row, every column and every three-by-three box contains the digits 1 to 9 exactly once, with no repeats in any of them. Nothing else is allowed and nothing else is needed: a correct sudoku never requires a guess, because at every stage some cell can be deduced from the digits already on the board. On this page the grid arrives mostly filled and only the marked cells are yours.
What is a good sudoku time?
There is no single good sudoku time, because it depends entirely on how many cells you fill. For the ten-cell Starter rounds on this page, internal test runs land between about 45 and 110 seconds of net time, and 75 seconds is the target that moves you up a difficulty. A full 81-cell grid is a different task and takes minutes rather than seconds. These are ranges from test runs, not a survey of players, so they cannot tell you how you compare with other people.
What sudoku techniques do you actually need?
Four techniques carry almost every puzzle here, and the difficulty names say which one is the ceiling: a row, column or box down to its last empty cell; a cell where only one digit still fits; a digit with only one place left in its unit; and ruling a digit out of a box because it is stuck on one line. No puzzle on this page needs anything beyond its tier's technique, and none needs a guess, so anything harder you find yourself doing is work you did not have to do.
What is the difference between easy and hard sudoku?
Two things move together: how many cells you have to fill, and the hardest technique the puzzle can demand. Here Starter is ten cells that fall to the simplest rule, and Expert is twenty-four that may need block elimination. A harder puzzle is not a denser grid; it is one where the next forced cell takes more looking for. That is also why times at different difficulties are never compared with each other on this page.
How do you get better at sudoku?
Stay on one difficulty until your times stop dropping, then let the ladder move you up. The single change that shortens most times is where you look: instead of asking what fits in this cell, ask which row, column or box is nearly full and take the cell it forces. Use notes on cells you are unsure about rather than trying a digit, since a wrong digit costs ten seconds and a note costs nothing. What gets faster with practice is your sudoku, and the honest way to see it is your own earlier rounds at the same difficulty.
What mistakes do sudoku beginners make?
The three common ones are guessing a digit to see whether it sticks, scanning cell by cell instead of unit by unit, and chasing the cell that looks interesting rather than the one that is already forced. The first is the expensive one here: a wrong digit never enters the cell, but it adds ten seconds to your net time, and six wrong digits in the same cell ends the round without a time. If you cannot name the row, column or box that proves a digit, take a hint instead of a guess.
Does every sudoku have only one solution?
A valid sudoku has exactly one solution, and every puzzle on this page is counted by a solver before it ships. A grid with two solutions is broken: at some point you can no longer deduce which digit belongs and have to guess, and if you guess the other legal answer you get marked wrong for being right. That is also why a genuine sudoku never needs trial and error.
Does playing sudoku train logical thinking?
What reliably improves is your sudoku: you spot patterns faster, take fewer wrong turns and scan units instead of cells. Evidence that this carries over to reasoning at work or in daily life is much weaker, so treat the time here as a reading of this task on this day, not as a reading of you. Play it because the puzzle is worth solving, and use the times to compare yourself with yourself.
Related games
ThinkingCode BreakerGuess the hidden colour code. Every guess comes back with two numbers — how many pegs are exactly right, and how many are the right colour in the wrong place.PlayAbout 2 min
ThinkingTower of HanoiMove four disks to the right-hand peg, then compare your move count with the fixed 15-move shortest route.PlayAbout 1 min
MemoryDigit Span TestDigits flash one at a time. Type them back in order and see how long a string you can hold.PlayAbout 60s
MemoryVisual Memory TestMemorize lit cells on a 5×5 grid, tap the same positions after they disappear, and compare your weighted visual memory span across completed tests.Play1-2 minThis test is for self-understanding and practice only, not a clinical or intelligence diagnostic tool. It is a non-standardised timed adaptation of sudoku; its times cannot be used interchangeably with clinical assessment scores.
Last updated: 2026-09-16 · Scores stay on this device