Arrow Sudoku: rules, strategy and how to start
An arrow is arithmetic hiding inside a logic puzzle. The circled cell equals the sum of every digit along its shaft — which means at least one cell on the line must be small enough to leave room for the others.
Why the rule changes everything
Sums constrain the extremes. A circle holding 6 with two shaft cells forces pairs like 1+5, 2+4 or 3+3; a circle holding 9 needs 1+8, 2+7, 3+6 or 4+5. That is a short list, and sudoku usually cuts it to one.
The second effect is subtler: every shaft cell must be smaller than the circle. A circle of 3 instantly rules out 4–9 from its entire arm.
How to start a board
- Find the smallest circle on the board — it constrains the most cells.
- For a two-cell arrow, list the pairs that sum to the circle value and cross out the impossible ones.
- A shaft that runs through a box lets you use box rules to eliminate sums, not just individual digits.
Common mistakes
- Including the circle cell in its own sum.
- Assuming shaft digits must be distinct — repetition is legal unless a unit forbids it.
- Ignoring multi-cell shafts that pass through the same box twice.
Frequently asked questions
Can an arrow circle be 1 or 2?
No — a shaft needs at least one digit and must sum to the circle, so the minimum is 2.
Do arrows overlap?
They can, and overlapping shafts are the richest source of deductions on a hard board.
Every board on this site is generated with a uniqueness check, so the puzzle in front of you has exactly one solution and every digit can be proved rather than guessed.
Play Arrow Sudoku ↗