Classic Sudoku · 28
Classic Sudoku · 28: 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: R1C2 = 9
After the preceding deductions, row 1, column 2 has only candidate 9. Its row, column and box exclude every other digit. Enter 9, then update the remaining candidates; this conclusion does not require consulting the completed answer.
Check the existing digits: row 1: 1, 3, 8; column 2: 2, 4, 5, 6; box: 3, 6, 7, 8. Each digit already present rules out that candidate in this cell.
Deduction 2: R1C5 = 4
After the preceding deductions, row 1, column 5 has only candidate 4. Its row, column and box exclude every other digit. Enter 4, then update the remaining candidates; this conclusion does not require consulting the completed answer.
Check the existing digits: row 1: 1, 3, 8, 9; column 5: 2, 6, 7, 8, 9; box: 3, 5, 7, 8. Each digit already present rules out that candidate in this cell.
Deduction 3: R1C6 = 6
After the preceding deductions, row 1, column 6 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 1: 1, 3, 4, 8, 9; column 6: 2, 5, 7, 8; box: 3, 4, 5, 7, 8. Each digit already present rules out that candidate in this cell.
Deduction 4: R2C2 = 1
After the preceding deductions, row 2, column 2 has only candidate 1. Its row, column and box exclude every other digit. Enter 1, then update the remaining candidates; this conclusion does not require consulting the completed answer.
Check the existing digits: row 2: 4, 5, 7, 8; column 2: 2, 4, 5, 6, 9; box: 3, 6, 7, 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 2. From the starting grid, its legal candidates are 9. 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
5 · 9 · 8 · 3 · 4 · 6 · 1 · 2 · 72 · 1 · 7 · 5 · 8 · 9 · 6 · 3 · 43 · 6 · 4 · 2 · 7 · 1 · 9 · 5 · 88 · 5 · 1 · 4 · 9 · 3 · 2 · 7 · 67 · 2 · 6 · 8 · 1 · 5 · 3 · 4 · 94 · 3 · 9 · 7 · 6 · 2 · 5 · 8 · 11 · 8 · 2 · 9 · 5 · 4 · 7 · 6 · 39 · 4 · 5 · 6 · 3 · 7 · 8 · 1 · 26 · 7 · 3 · 1 · 2 · 8 · 4 · 9 · 5