Classic Sudoku · 15
Classic Sudoku · 15: 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: R2C1 = 7
After the preceding deductions, row 2, column 1 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 2: 2, 3, 4, 5; column 1: 1, 4, 6, 8, 9; box: 1, 8. Each digit already present rules out that candidate in this cell.
Deduction 2: R2C2 = 6
After the preceding deductions, row 2, column 2 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 2: 2, 3, 4, 5, 7; column 2: 8, 9; box: 1, 7, 8. Each digit already present rules out that candidate in this cell.
Deduction 3: R2C3 = 9
After the preceding deductions, row 2, column 3 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 2: 2, 3, 4, 5, 6, 7; column 3: 1, 3, 6, 8; box: 1, 6, 7, 8. Each digit already present rules out that candidate in this cell.
Deduction 4: R6C1 = 2
After the preceding deductions, row 6, column 1 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 6: 3, 5, 6, 9; column 1: 1, 4, 6, 7, 8, 9; box: 4, 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 2, column 1. 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 · 5 · 4 · 2 · 8 · 1 · 7 · 6 · 97 · 6 · 9 · 4 · 5 · 3 · 1 · 8 · 21 · 8 · 2 · 9 · 6 · 7 · 3 · 5 · 49 · 3 · 5 · 8 · 1 · 4 · 2 · 7 · 64 · 1 · 8 · 6 · 7 · 2 · 9 · 3 · 52 · 7 · 6 · 5 · 3 · 9 · 4 · 1 · 88 · 2 · 7 · 3 · 9 · 6 · 5 · 4 · 15 · 4 · 1 · 7 · 2 · 8 · 6 · 9 · 36 · 9 · 3 · 1 · 4 · 5 · 8 · 2 · 7