Math sudoku variants (maths variants, in Commonwealth spelling) add arithmetic constraints to the classic logic puzzle. Instead of relying solely on elimination and placement, these puzzles ask you to think about sums and number combinations. This page compares the main families: Killer Sudoku, Sum Sudoku and Kakuro hybrids.
Killer Sudoku uses the standard 9x9 grid but removes the given digits. Cells are grouped into outlined cages, each with a target sum, and no digit repeats inside a cage. For the full walkthrough, read Killer Sudoku rules. To speed up your first pass, use the combinations chart.
Sum Sudoku is a broader category that includes Killer Sudoku and its variations. Some versions allow digit repetition within cages, while others use different cage shapes or overlapping regions. The core idea stays the same: cells are grouped, and their digits must reach a target sum.
Kakuro is a crossword-style number puzzle where clues are sums for horizontal and vertical runs. Kakuro-Sudoku hybrids combine the 9x9 Sudoku grid with Kakuro-style sum clues along the edges or within the grid. These puzzles tend to be complex and appeal to solvers who enjoy both formats.
Solving math variants needs a different approach from classic Sudoku:
{8, 9}. A two-cell cage summing to 3 must be {1, 2}.Math variants are generally harder than classic Sudoku because they add a layer of numerical reasoning. Killer Sudoku sits closest to classic play, since the standard rules all still apply. Sum Sudoku variants with unusual cage rules and Kakuro hybrids ask for more new habits, so they suit solvers who already enjoy sums.
If you are comfortable with medium-to-hard classic Sudoku, Killer Sudoku is a natural next step. Start with puzzles that have smaller cages, which give more constraints and are easier to solve.