Number & arithmetic

Killer Sudoku — rules and where to play

KILLER SUDOKU · Sumdoku / Addoku / Samunamupure

Standard Sudoku plus dotted cages whose digits add to a corner total. It welds elimination onto addition, and it is the most popular variant by a wide margin.

Origin: 1995 · Japan
Difficulty: ★★★★★ 3–5 / 5
Time: 15–90 min
Grid: 9×9
Sites: 9

Rules

All standard Sudoku rules apply.
Digits inside a dotted cage sum to the small number printed at its corner.
No digit repeats inside a single cage.

How to start

Memorise the small cage combinations

Two cells summing to 3 means 1+2; 17 means 8+9. Three cells at 6 means 1+2+3; at 24 means 7+8+9. These are free cells.

Cut corners with the 45 rule

Every row, column and box totals 45. Subtract the fully contained cages from a box and the remainder is your opening.

No repeats inside a cage is a strong constraint

A two-cell cage summing to 6 can never be 3+3.

Where players get stuck

Applying the 45 rule to cages that straddle a box border and getting a wrong figure.
Forgetting the no-repeat rule and writing 4+4.

Play Killer Sudoku

9 sites

f-puzzlesFree

The default web editor for Sudoku variants. Build a grid, send the link, or just solve.

Open → Killer Sudoku OnlineFree

Killer only. New grids by the day and the week, and they get meaner as they go.

Open → Daily Killer SudokuFree

One new Killer a day, plus a few extras. Nothing to pay.

Open → Killer SudokuFree

Killer Sudoku that's been around. An online solver, and a deep pile of old grids.

Open → SudokuPadFree

The variant player a lot of people use now, and it edits too. There's an app and a Steam build.

Open → Penpa+Free

A fat editor for Japanese types: lots of shapes and marks, and it will ingest a puzz.link.

Open → Puzzle Killer SudokuFreemium

Puzzle Team Killer Sudoku: cage sums on top of classic Sudoku rules.

Open → Grandmaster PuzzlesFree

Thomas Snyder's own handmade Sudoku and variants — world-champion difficulty, not generated filler.

Open → GridPuzzleFree

Dozens of grid logic types in the browser, with progress tracking and dailies.

Open →

Browse Solvers & tools →

Also on multi-type portals

KrazydadFree

Jim Bumgardner’s printable library. Sudoku and other books as PDFs — made for a bag and a pencil.

Open → Printable SudokuFree

Blank Sudoku sheets in every grade, meant for paper.

Open → Puzzle RulesFree

Clean rule pages for dozens of types. Fastest way to learn a grid you haven't seen.