Calcudoku online

In Calcudoku online you fill a grid with the digits 1 to n so that no digit repeats in any row or column. In addition, each heavily outlined cage gives an arithmetic target such as “12×” or “3−”. Choose the size (4 × 4 to 7 × 7) and the operations; every puzzle has exactly one solution. No sign-up, works on phones.

Source: Wikipedia: KenKen (rules of the arithmetic sudoku family, inventor Tetsuya Miyamoto, 2004). Updated: 2 October 2026.

How it is calculated

In short: Calcudoku (also called math Sudoku or Mathdoku) is a number puzzle that combines Sudoku with mental arithmetic. You place the digits 1 to n so that each appears once in every row and column – and every heavily outlined cage reaches its arithmetic target.

How to read the cages

Clue	Meaning	Example
5	Single square: the digit is given	5
7+	Sum of the digits in the cage	3 + 4
3−	Difference of two digits (larger minus smaller)	5 − 2
12×	Product of the digits in the cage	3 × 4
2÷	Quotient of two digits (larger divided by smaller)	6 ÷ 3

The clue sits in small print in the top-left corner of the cage. Cages with minus or divide always have exactly two squares.

Solving tips

Single squares first: they are free and remove that digit from the row and column.
Break down products: a two-square cage “6×” can only hold 1 and 6 or 2 and 3; on a 4 × 4 grid the 6 is out, so it is 2 and 3.
Narrow down sums: “3+” over two squares is only 1 and 2. Over three squares “6+” is only 1, 2 and 3.
Row and column logic: if a cage lies in one row, its digits must differ. Use notes to keep track of candidates.

Sizes and operations

“Plus and minus” is the gentle start, “Plus, minus, times, divide” the full version. From 4 × 4 for a quick break to 7 × 7 for longer sessions; the program checks every puzzle for exactly one solution.

Puzzle series

“Next puzzle” takes you through a numbered series. Size, operations and number define the puzzle exactly, so you can pass it on. Your progress stays on your device only.

Frequently asked questions

How does Calcudoku work?

You fill an n × n grid with the digits 1 to n, each once per row and column. The heavily outlined cages give a number and an operator that their digits must produce.

Do I have to guess in Calcudoku?

No. Every puzzle has exactly one solution that can be found by reasoning. The hint places a correct digit if you get stuck.

Can digits repeat inside a cage?

Yes, but only if the squares share neither a row nor a column. Otherwise the row or column rule would be broken.

How is it different from Sudoku?

Instead of 3 × 3 boxes there are arithmetic cages, so mental arithmetic matters: you break down sums, differences, products and quotients.

Is anything saved?

Only which puzzle numbers you solved, and only in your browser (localStorage). Nothing is sent anywhere.

Sources and legal basis

As of: 2 October 2026 · Editorial policy