Classic Sudoku · 30
Classic Sudoku · 30: a 9×9 Sudoku with 36 clues and one solution. Play online, use pencil notes and hints, or compare the complete answer.
Use rows and columns: R1C1 is row 1, column 1. Enter digits inside the squares.
Read the position, one decision at a time
Follow the deductions in order. Each step uses the grid after the preceding entry.
Reveal step-by-step explanations
Deduction 1: R1C4 = 7
After the preceding deductions, row 1, column 4 has only candidate 7. Its row, column and box exclude every other digit. Enter 7, then update the remaining candidates; this conclusion does not require consulting the completed answer.
Check the existing digits: row 1: 5, 6, 9; column 4: 1, 2, 4, 8, 9; box: 2, 3, 8, 9. Each digit already present rules out that candidate in this cell.
Deduction 2: R3C7 = 2
After the preceding deductions, row 3, column 7 has only candidate 2. Its row, column and box exclude every other digit. Enter 2, then update the remaining candidates; this conclusion does not require consulting the completed answer.
Check the existing digits: row 3: 4, 7, 8, 9; column 7: 1, 3, 5, 6, 9; box: 5, 6, 9. Each digit already present rules out that candidate in this cell.
Deduction 3: R5C4 = 6
After the preceding deductions, row 5, column 4 has only candidate 6. Its row, column and box exclude every other digit. Enter 6, then update the remaining candidates; this conclusion does not require consulting the completed answer.
Check the existing digits: row 5: 3, 4, 5, 8, 9; column 4: 1, 2, 4, 7, 8, 9; box: 4, 5, 8, 9. Each digit already present rules out that candidate in this cell.
Deduction 4: R6C4 = 3
After the preceding deductions, row 6, column 4 has only candidate 3. Its row, column and box exclude every other digit. Enter 3, then update the remaining candidates; this conclusion does not require consulting the completed answer.
Check the existing digits: row 6: 5, 7, 8, 9; column 4: 1, 2, 4, 6, 7, 8, 9; box: 4, 5, 6, 8, 9. Each digit already present rules out that candidate in this cell.
Understand this position
9×9 grid · 3×3 boxes · 36 clues · 45 empty cells
Start by inspecting row 1, column 4. From the starting grid, its legal candidates are 7. Check the filled digits in that row, column and box before entering a number. Only one candidate remains: this is a naked single.
Read the complete answer by row
3 · 2 · 1 · 7 · 9 · 4 · 8 · 5 · 66 · 8 · 5 · 2 · 3 · 1 · 7 · 4 · 99 · 7 · 4 · 8 · 6 · 5 · 2 · 1 · 35 · 3 · 8 · 9 · 1 · 2 · 6 · 7 · 41 · 9 · 2 · 6 · 4 · 7 · 3 · 8 · 54 · 6 · 7 · 3 · 5 · 8 · 9 · 2 · 12 · 4 · 9 · 5 · 7 · 6 · 1 · 3 · 87 · 5 · 6 · 1 · 8 · 3 · 4 · 9 · 28 · 1 · 3 · 4 · 2 · 9 · 5 · 6 · 7