Sudoku Written by Brian Hamilton and Karan Hamilton.
Brian and Karan are the puzzle lovers and game makers behind Sudoku Online Puzzles. You can learn more on the About page.
Guides are reviewed for clarity, accuracy, and usefulness for solvers. See our editorial standards, puzzle testing process, or send a correction.
Sudoku asks for one thing: each digit once in every row, column and box, with every placement proved from what is already on the grid. Plenty of other puzzles ask for the same kind of proof. Some keep sudoku’s row-and-column rule and drop the boxes. Some keep the sums you juggle in Killer Sudoku. Some keep nothing but the habit of crossing out possibilities until one is left.
So instead of ranking them, we have sorted eleven well-known puzzles by what they keep from sudoku. For several of them there is a bridge on this site: a sudoku that borrows the other puzzle’s rule, so you can meet the idea on a grid you already know. The outside puzzles’ rules and history come from the sources linked in each section; what we say about our own games comes from their code and from boards we dealt and measured.
What is the closest game to sudoku?
The puzzles that share the most with sudoku are the Latin-square puzzles: KenKen, Futoshiki and Skyscrapers. Each keeps sudoku’s main rule, every number once in each row and each column, and takes away the 3×3 boxes. A different clue stands in for them: arithmetic cages in KenKen, greater-than signs in Futoshiki, sightlines in Skyscrapers.
If you would rather keep the boxes and change one thing, that is a sudoku variant rather than another game, and our sudoku variations list covers those. The smallest step is Jigsaw Sudoku, where the boxes become irregular shapes and every other rule stays.
A Latin square is a grid of n rows and n columns holding n symbols, each once in every row and once in every column. A finished sudoku is a 9×9 Latin square that also passes the box rule. KenKen, Futoshiki and Skyscrapers answers are Latin squares with no box rule; Wikipedia’s Futoshiki article puts it plainly: “A solved futoshiki puzzle is a Latin square.”
| Puzzle | What it keeps from sudoku | What it changes | Closest game here |
|---|---|---|---|
| KenKen (Calcudoku) | Each number once per row and column | No boxes; cages with a target and +, −, × or ÷ | Calcudoku (the same rules) |
| Kakuro | Digits 1–9, no repeat within a group | Crossword-shaped grid; each run adds up to its clue | Killer Sudoku |
| Futoshiki | The Latin square | No boxes; < and > signs between neighbours | Greater Than Sudoku |
| Skyscrapers | The Latin square | No boxes; edge clues count the towers in view | Skyscraper Sudoku |
| Hitori | No number twice in a row or column | You black out numbers instead of writing them | — |
| Solitaire Battleships | Row and column counts; pure deduction | A hidden fleet instead of digits | Battleship Sudoku |
| Queens (LinkedIn) | One of something per row and column | One crown per coloured region, none touching | Dedoku |
| Logic grid puzzles | A grid of what is still possible | Written clues about people, places and times | Dedoku |
| Nonograms | Line-by-line reasoning | Edge clues give runs of shaded squares; the answer is a picture | — |
| Slitherlink | Number clues; you work from what is forced | You draw a single loop round the numbers | — |
| Minesweeper | Number clues about neighbours | Hidden mines, and not every version avoids a guess | — |
The last column names the game on this site that borrows each puzzle’s rule; Calcudoku is the only one with exactly the same rules, and the others put the rule on a sudoku grid. The outside puzzles’ rules are from the sources linked in the sections below, checked October 2026.
Is KenKen the same as Calcudoku?
Yes. KenKen was invented in 2004 by the Japanese maths teacher Tetsuya Miyamoto. KenKen and KenDoku are trademarks; Calcudoku and Mathdoku are the names used by those without the rights to them (Wikipedia, KenKen). The Times in London began printing the puzzles in March 2008, and other papers, The New York Times among them, followed.
The rules: fill an n×n grid so that every row and column holds 1 to n once. Heavy outlines cut it into cages, each with a target and an operation, and the cage’s digits must make the target with that operation. A cage may repeat a digit, as long as the two copies share no row or column, which is the rule newcomers most often trip on.
Our Calcudoku deals grids from 4×4 to 9×9 at four levels, and the levels are the operations. Easy only adds, Medium adds subtraction, Hard multiplication and Expert division, with cages of up to two squares on Easy, three on Medium and four from Hard on. Before a board reaches you, the generator checks that two plain steps finish it: keeping in each square only the digits some way of making its cage allows, and placing singles. A board those steps finish has exactly one answer. One they don’t is thrown away and drawn again.
Is Kakuro like sudoku?
Kakuro looks like a crossword filled with digits. Black squares carry the clues, and each run of white squares beside a clue must add up to it, using the digits 1 to 9 with no digit twice in the run (Wikipedia, Kakuro). There are no boxes and no full rows to fill; a run can be anything from two squares to nine.
In English it began as Cross Sums, the name Jacob E. Funk of Dell Magazines gave it in 1966. The Japanese name is short for kasan kurosu, “addition cross”, and Wikipedia records that Kakuro “remained the most popular logic puzzle in Japanese printed press until 1992, when Sudoku took the top spot.”
What Kakuro shares with sudoku is less the grid than the arithmetic of sets. A two-square run of 3 can only be 1 and 2; a four-square run of 30 can only be 6, 7, 8 and 9. Killer Sudoku cages follow the same rule, 1 to 9 with no repeat inside a cage, so one chart of combinations serves both puzzles: our killer sudoku combinations chart lists every cage size from one square to nine. Killer adds what Kakuro lacks, rows, columns and boxes that each hold 1 to 9, and with them the rule of 45. Its cages can also bend round corners, where a Kakuro run is always straight.
Which puzzles like sudoku use numbers but no arithmetic?
Futoshiki, Japanese for “inequality”, was developed by Tamaki Seto in 2001. It is a Latin square with some digits given and a < or > sign between some pairs of neighbouring squares (Wikipedia, Futoshiki); Wikipedia lists The Guardian on Saturdays and The Times daily among the British papers that print it. Our Greater Than Sudoku puts Futoshiki’s signs on a full sudoku. A 9×9 grid has 144 pairs of neighbouring squares, and across 40 boards per level, Easy shows 100 signs with 36 digits and Expert 32 signs with 21 digits. Every board is built so the signs matter: without them, the digits on an Easy board allow a median of 4 answers, and on Hard and Expert 200 or more.
Skyscrapers is a Latin square where each number is a building’s height, and “taller buildings block the view of smaller buildings.” The clues round the edge say how many buildings you can see from that side. GMPuzzles calls it “a Japanese creation” that first reached a wide audience at the 1992 World Puzzle Championship in New York, and says its original author is unknown (GMPuzzles, Skyscrapers rules). Skyscraper Sudoku sets those clues round a 9×9 sudoku, with room for 36 of them. Easy shows all 36 and Expert 20, and each board is proved to have one answer under the clues shown before it is dealt.
Hitori starts with a grid that is already full of numbers. You black some out so that no number appears twice in a row or column, no two black squares touch side by side, and the white squares stay connected to one another. It is a Nikoli original, first printed in Puzzle Communication Nikoli in March 1990 (Wikipedia, Hitori). Think of it as sudoku’s no-repeat rule run backwards: you remove duplicates instead of avoiding them.
Which logic puzzles are like sudoku without the digits?
Solitaire Battleships hides a fleet in a 10×10 grid: one battleship four squares long, two cruisers of three, three destroyers of two and four submarines of one, no two ships touching, not even diagonally. The number beside each row and column says how many of its squares are ship. It was invented in Argentina by Jaime Poniachik, first published in 1982 in the magazine Humor & Juegos, and made its international debut at the first World Puzzle Championship, in New York in 1992 (Wikipedia, Battleship puzzle). Battleship Sudoku hides that same fleet in a 9×9 sudoku, so you solve two puzzles on one grid. Our generator proves that the digits and the fleet each have exactly one answer, and chooses the ship squares it shows so the fleet can be reasoned out without trial and error.
Queens, LinkedIn’s daily puzzle, asks for one crown in each row, each column and each coloured region, with no two crowns in neighbouring squares, diagonals included. A new one appears every day at midnight Pacific time (LinkedIn Help, Queens, as of October 2026). Sudoku players know the shape already: in a finished sudoku, the nine 5s also sit one to a row, one to a column and one to a box.
Logic grid puzzles give you a short story and a list of clues and ask who did what, where and when; you tick and cross a grid of possibilities until one arrangement is left. Dedoku, the detective game on this site, sets that kind of case on a floor plan: a few witnesses and one missing item, clues about rooms and furniture, and one rule borrowed from sudoku, one case piece per row and per column. It is the same shape as a Queens answer, except that every mark is a different witness or the missing item, so the question is who as well as where.
Clues do most of Dedoku’s eliminating, so we checked whether the borrowed rule matters. We ran the game’s own solver over 47 cases from its generator, once as shipped and once with the one-per-row-and-column rule switched off. Without the rule it finished none of the 36 Easy, Medium and Hard cases; only Expert, whose clues give exact offsets, could finish some, 6 of 11. A fresh run of 18 Easy and Hard cases in October 2026 agreed: every one finished with the rule, none without it.
Are Nonograms and Slitherlink like sudoku?
Nonograms, also sold as Picross, Griddlers and Hanjie, give each row and column a list of numbers: the lengths of the runs of shaded squares in it, in order. Shade the right squares and a picture appears. Non Ishida, a Japanese graphics editor, developed the idea in 1987, and the puzzler Tetsuya Nishio invented the same puzzles independently. Picross is Nintendo’s trademark; Griddlers was the name readers of The Sunday Telegraph chose in a 1998 contest (Wikipedia, Nonogram). The rhythm is sudoku’s: work one line at a time and fill in only what every possible arrangement agrees on.
Slitherlink, a Nikoli original from June 1989, has you draw one loop along the dotted lines of a grid, and each number says how many of its four sides the loop uses (Wikipedia, Slitherlink). There is no digit to place, but the opening is pure sudoku habit: start from the clues that leave the least choice, such as a 0, whose four sides all stay empty, and build out from there.
Is Minesweeper a game like sudoku?
Partly. Each number you uncover says how many of the eight squares around it hide a mine, and good play is deduction from those numbers (Wikipedia, Minesweeper). The difference is the promise. A properly made sudoku has exactly one answer, so every square can in principle be reasoned out. Some versions promise that your first click is safe, which is not the same as promising a board you can clear without guessing. Simon Tatham’s free Mines makes the stronger promise by default: “you are guaranteed to be able to solve the whole grid by deduction rather than guesswork” (Simon Tatham’s Mines). If a forced coin-flip near the end spoils it for you, look for a version that says the same.
Which game like sudoku should you try first?
Start from the part of sudoku you enjoy most:
- The arithmetic in Killer Sudoku: Calcudoku at Hard, where multiplication arrives, then Kakuro.
- Sudoku without any maths: Greater Than Sudoku, then Futoshiki, which is the same reasoning with the boxes taken away. Skyscraper Sudoku and Skyscrapers pair up the same way.
- Pictures rather than numbers: Nonograms.
- A story to solve: Dedoku, or a book of logic grid puzzles.
- A few minutes a day: Queens, or our daily sudoku: one puzzle a day, the same for everyone, Easy on Monday and Tuesday, Medium midweek, Hard on Friday and Expert at the weekend.
A rule is easiest to learn where everything else is already second nature. On Easy Greater Than Sudoku, our solver finishes all 40 of the boards we measured with nothing but the signs and singles, and stalls on all 40 if it ignores the signs. So you learn to read a chain of < and > with nothing harder going on around it. Once that is automatic, a Futoshiki is the same skill with fewer houses to lean on.
And if what you want is more sudoku rather than a different game, the variants keep everything you know and add one rule each: diagonals in X-Sudoku, five overlapping grids in Samurai Sudoku, lines in Thermo Sudoku and Arrow Sudoku, letters in Wordoku. For a gentler start, 4×4 and 6×6 sudoku teach the same rules on a smaller board.