Welcome to Calcudoku!

Calcudoku is a fun logic puzzle that extends beyond the traditional confines of Sudoku by integrating math into the mix. The game was invented by Japanese math teacher Tetsuya Miyamoto in order to help his students learn math. The game is also known as “KenKen” of Mathdoku. The goal of each Calcudoku puzzle is to fill in the grid with the digits 1 through N (where N is the number of rows or columns in the grid) such that no column or row contains the same number twice. While a number may repeat within a block, the numbers within the block must produce the result of the mathematical operation appearing in the block. The game is a test of both numerical skill and logical reasoning, offering a rich problem-solving experience that can be stimulating for those seeking a challenge beyond traditional puzzles.

The Basics

The Grid: Calcudoku is played on a square grid consisting of an equal number of rows and columns. The smallest grid is typically 4×4 and the largest is 9×9. However, the most common sizes are 5×5 and 6×6 grids.

The Blocks: The blocks are groups of squares over which an arithmetic operation will apply. Unlike Killer Sudoku, numbers may repeat within a block as long as they are not in the same row or column.

Arithmetic Clues: In each block is a numerical value followed by an arithmetic sign (+ – x ÷). The arithmetic operation will apply to the numbers you fill in each block with. The result of the operation must be the numerical value specified.

Calcudoku Rules

In a Calcudoku puzzle, you will be presented with an NxN grid.  You must fill out the grid using the numbers 1 to N and the following rules must be adhered to:

• Use all digits 1 to N in each row and column
• No digit may repeat within a row or column
• The numbers within a block must result in the numerical value specified in the block when the arithmetic operation is applied
• A digit within a block may repeat as long as it does not repeat in the same row or column
• The puzzle is solved when all cells in the grid are filled in without violating any rules

Useful tips

• Pencil and eraser are your friend!
  Make sure you use a sharp pencil with an eraser. When you first start solving Calcudoku puzzles, you are likely to make mistakes. Even seasoned Calcudoku puzzlers make mistakes.
• Pace yourself
  Accuracy is more important than speed. The more accurate you are as you solve the puzzle, the less likely you are to makes mistakes. If you make a mistake, sometimes you can recover easily. However, if the mistake is one you don’t catch until the puzzle is almost complete, you may need to backtrack all the way to the beginning. And don’t worry, as you solve more Calcudoku puzzles, you will get better at applying your logic and your speed will organically increase.
• Approach each puzzle systematically
  Start with the obvious and move to the more difficult parts of the puzzle. For instance, it is better to start with a row, column, or sub-grid that is mostly complete than one with a single number. Or starting with a number that occurs frequently in the puzzle already rather than a number that occurs once.
• Practice, practice and practice!
  Calcudoku is about applying math, logic, and problem solving skills. These are skills we all have on some level, but new skills take time to develop. The more you practice and play Calcudoku puzzles, the better you will get at accessing the logic you’ve learned and applying that logic to solving them regardless how difficult.
• Use a notation system
  As you begin to solve Calcudoku puzzles, find a useful notation system that works for you. Then as you play, use this notation system to keep track of all the decisions you make as you apply your logic and math skills.