Futoshiki
Fill the grid so every row and column contains each digit exactly once. Inequality symbols between cells must be satisfied. Also known as greater-than sudoku.
Futoshiki
5×5 grid. More constraints. Cross-elimination needed.
Standard play. Timer runs. Hints available.
What is Futoshiki?
Futoshiki is a Japanese logic puzzle where you fill an N×N grid with digits 1 through N so that each row and column contains every digit exactly once. Between some adjacent cells, inequality symbols (< > ∧ ∨) constrain which cell must hold the larger value. The combination of Latin square constraints and inequality clues creates a puzzle that's different from sudoku in a satisfying way: you reason about relative size, not just uniqueness.
The name translates roughly to "not equal" in Japanese. Futoshiki is also known as greater-than sudoku, unequal, or the inequality puzzle. Grid sizes range from 4×4 for beginners to 9×9 for experts. Every puzzle on this site has exactly one solution and is solvable through logic alone.
How to play
Tap a cell to select it, then tap a number to place it. Inequality symbols sit between cells: < and > for horizontal pairs, ∧ and ∨ for vertical pairs. A < symbol means the left cell must be less than the right cell. ∧ means the top cell must be less than the bottom cell.
Use notes mode to track candidate digits. The hint system points you toward a solvable cell with an explanation of the technique used. If you get stuck, reveal the solution and study which constraint would have unlocked the next step.
How to solve Futoshiki
Technique by technique, beginner to advanced.
Naked singles
When row, column, and inequality constraints eliminate all but one digit for a cell, place it. In a 4×4 grid, if row 1 already has 1, 2, and 3, the remaining cell must be 4. Naked singles are the most common technique and often trigger chain reactions.
Inequality forcing
If cell A < cell B, then A cannot hold the maximum digit and B cannot hold 1. In a 4×4 grid with A < B, A can be at most 3 and B is at least 2. When A already has candidates {3, 4} and the < constraint applies, A must be 3.
Inequality chains
Follow chains of inequality symbols: if A < B < C in a 4×4 grid, then A ≤ 2, B can be 2 or 3, and C ≥ 3. Longer chains narrow candidates more aggressively. In a chain of length 3 within a 4×4 grid, the first cell is forced to 1 and the last to 4.
Hidden singles
If a digit can only appear in one cell within a row or column, place it there. Unlike naked singles (one candidate for a cell), hidden singles are one cell for a digit. After applying inequality constraints, check each row and column for digits with a single valid position.
Difficulty levels
| Level | Grid | Key techniques |
|---|---|---|
| Easy | 4×4 | Naked singles, basic inequality |
| Medium | 5×5 | Inequality forcing, cross-elimination |
| Hard | 6×6 | Inequality chains, hidden singles |
| Expert | 7×7–8×8 | Advanced propagation, multi-chain deduction |
| Einstein | 8×8–9×9 | Logic-only, no guessing required |