Fill each row and column with unique numbers. Follow the inequality signs — they always tell the truth.
Futoshiki means "inequality" in Japanese and was popularized in Western newspapers as an alternative to Sudoku. It is a logic-based number puzzle where you fill an N×N grid so that every row and column contains each number from 1 to N exactly once, while respecting greater-than and less-than constraints between adjacent cells. Over the last decade, Futoshiki has gained a devoted following among puzzle enthusiasts seeking a fresh challenge beyond traditional Sudoku.
Choose your grid size (4×4, 5×5, or 6×6) and difficulty level. The grid comes with some numbers pre-filled and inequality signs between certain pairs of adjacent cells. Use logic to fill in the missing numbers: each row and column must contain unique numbers, and every inequality must be satisfied. Features include pencil marks for noting candidates, undo, error checking, and a timer to track your solving speed.
While both are number-placement logic puzzles, Futoshiki uses inequality constraints (greater-than and less-than signs) between adjacent cells instead of Sudoku's 3×3 box rule. Futoshiki grids are typically smaller and the inequalities add a unique layer of deduction not found in Sudoku.
Start by identifying cells at the ends of inequality chains — the largest or smallest values are often forced. Use elimination: if a cell must be greater than its neighbor, remove impossible candidates. Also look for rows or columns where only one number can fit in a given position.
No. A well-constructed Futoshiki puzzle can always be solved through pure logic. Every puzzle on whatifs.fun has a unique solution reachable by logical deduction alone, without trial and error.
If you enjoyed this, try these: Sudoku · KenKen · Kakuro
Last updated: April 2026 · whatifs.fun — Free interactive games, experiments & simulations