Sudoku variant · rules and tips

Killer Sudoku

Each dotted cage carries a sum. The digits inside must add up to it, and no digit may appear twice within the same cage. Arithmetic, it turns out, is a form of deduction wearing a disguise.

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Professor Cryptic, the owl who teaches in the app
Professor Cryptic explains the rule

The Professor's tips

How do you solve Killer Sudoku?

01 / Warm up

Start on a 4 by 4 grid

  • A two-cell cage summing to 3 can only be 1 and 2. On a small grid the arithmetic does most of the thinking, so let it.
  • When a cage admits only one combination, pencil those digits in at once. You have earned that information. Spend it.
  • A cage that straddles two boxes tells you twice as much, because the digit may repeat in neither the cage nor the box.
02 / Level up

Then try a 6 by 6 grid

  • Do the sums before you do anything rash. A three-cell cage totalling 6 with digits 1 to 6 can only be 1, 2 and 3.
  • If two cages between them cover a whole row, their sums plus any givens must total 21, since 1+2+3+4+5+6 = 21. The row cannot argue with that.
  • A cage cannot repeat, so a two-cell cage summing to 4 is not 2 and 2. It is 1 and 3, and there is nothing more to discuss.
  • Watch for cages that poke out of a box by a single cell. That overhang can often be calculated exactly. Solvers call them innies and outies, which is about as whimsical as the profession gets.

The rule, drawn

What does Killer Sudoku look like?

  1. Killer Sudoku rule illustration, step 1 of 3
  2. Killer Sudoku rule illustration, step 2 of 3
  3. Killer Sudoku rule illustration, step 3 of 3

Start with a single square

Where can you play Killer Sudoku?

Killer Sudoku is one of the 17 variants in Cryptic, each with a lesson and unlimited puzzles.

Get it onGoogle PlayPlay on the web