Step 0

Starting puzzle

1 2 3 4 5 6 7 8 9
A                 9
B 2     5     3 1 8
C 1   6 4         5
D       7     5    
E     8   3   6    
F     1     4      
G 6         1 7   2
H 7 2 3     9     4
I 4                

Step 1

The number 4 does not yet appear in row G. Due to other 4s on the grid, the only place it can go is cell G5.

1 2 3 4 5 6 7 8 9
A                 9
B 2     5     3 1 8
C 1   6 4         5
D       7     5    
E     8   3   6    
F     1     4      
G 6       4 1 7   2
H 7 2 3     9     4
I 4                

Step 2

The number 1 does not yet appear in column 2. Due to other 1s on the grid, the only place it can go is cell I2.

1 2 3 4 5 6 7 8 9
A                 9
B 2     5     3 1 8
C 1   6 4         5
D       7     5    
E     8   3   6    
F     1     4      
G 6       4 1 7   2
H 7 2 3     9     4
I 4 1              

Step 3

Because of the number 1 just placed, the only position in row H for another 1 is cell H7.

1 2 3 4 5 6 7 8 9
A                 9
B 2     5     3 1 8
C 1   6 4         5
D       7     5    
E     8   3   6    
F     1     4      
G 6       4 1 7   2
H 7 2 3     9 1   4
I 4 1              

Step 4

The number 2 does not yet appear in column 3. Due to other 2s on the grid, the only place it can go is cell D3.

1 2 3 4 5 6 7 8 9
A                 9
B 2     5     3 1 8
C 1   6 4         5
D     2 7     5    
E     8   3   6    
F     1     4      
G 6       4 1 7   2
H 7 2 3     9 1   4
I 4 1              

Step 5

The number 8 is missing from box G1-I3 and its only possible position is cell G2.

1 2 3 4 5 6 7 8 9
A                 9
B 2     5     3 1 8
C 1   6 4         5
D     2 7     5    
E     8   3   6    
F     1     4      
G 6 8     4 1 7   2
H 7 2 3     9 1   4
I 4 1              

Step 6

Because of the number 8 just placed, the only position in column 1 for another 8 is cell A1.

1 2 3 4 5 6 7 8 9
A 8               9
B 2     5     3 1 8
C 1   6 4         5
D     2 7     5    
E     8   3   6    
F     1     4      
G 6 8     4 1 7   2
H 7 2 3     9 1   4
I 4 1              

Step 7

The number 6 is missing from box A7-C9 and its only possible position is cell A8.

1 2 3 4 5 6 7 8 9
A 8             6 9
B 2     5     3 1 8
C 1   6 4         5
D     2 7     5    
E     8   3   6    
F     1     4      
G 6 8     4 1 7   2
H 7 2 3     9 1   4
I 4 1              

Step 8

Because of the number 6 just placed, the only position in column 9 for another 6 is cell I9.

1 2 3 4 5 6 7 8 9
A 8             6 9
B 2     5     3 1 8
C 1   6 4         5
D     2 7     5    
E     8   3   6    
F     1     4      
G 6 8     4 1 7   2
H 7 2 3     9 1   4
I 4 1             6

Step 9

The number 4 is missing from box A7-C9 and its only possible position is cell A7.

1 2 3 4 5 6 7 8 9
A 8           4 6 9
B 2     5     3 1 8
C 1   6 4         5
D     2 7     5    
E     8   3   6    
F     1     4      
G 6 8     4 1 7   2
H 7 2 3     9 1   4
I 4 1             6

Step 10

The number 7 is missing from box A7-C9 and its only possible position is cell C8.

1 2 3 4 5 6 7 8 9
A 8           4 6 9
B 2     5     3 1 8
C 1   6 4       7 5
D     2 7     5    
E     8   3   6    
F     1     4      
G 6 8     4 1 7   2
H 7 2 3     9 1   4
I 4 1             6

Step 11

C7 is the last empty cell in box A7-C9 and the missing number is 2.

1 2 3 4 5 6 7 8 9
A 8           4 6 9
B 2     5     3 1 8
C 1   6 4     2 7 5
D     2 7     5    
E     8   3   6    
F     1     4      
G 6 8     4 1 7   2
H 7 2 3     9 1   4
I 4 1             6

Step 12

The number 4 is missing from column 3 and its only possible position is cell B3.

1 2 3 4 5 6 7 8 9
A 8           4 6 9
B 2   4 5     3 1 8
C 1   6 4     2 7 5
D     2 7     5    
E     8   3   6    
F     1     4      
G 6 8     4 1 7   2
H 7 2 3     9 1   4
I 4 1             6

Step 13

The number 7 is missing from column 3 and its only possible position is cell A3.

1 2 3 4 5 6 7 8 9
A 8   7       4 6 9
B 2   4 5     3 1 8
C 1   6 4     2 7 5
D     2 7     5    
E     8   3   6    
F     1     4      
G 6 8     4 1 7   2
H 7 2 3     9 1   4
I 4 1             6

Step 14

The number 5 does not yet appear in row A. Due to other 5s on the grid, the only place it can go is cell A2.

1 2 3 4 5 6 7 8 9
A 8 5 7       4 6 9
B 2   4 5     3 1 8
C 1   6 4     2 7 5
D     2 7     5    
E     8   3   6    
F     1     4      
G 6 8     4 1 7   2
H 7 2 3     9 1   4
I 4 1             6

Step 15

The number 3 is missing from box A1-C3 and its only possible position is cell C2.

1 2 3 4 5 6 7 8 9
A 8 5 7       4 6 9
B 2   4 5     3 1 8
C 1 3 6 4     2 7 5
D     2 7     5    
E     8   3   6    
F     1     4      
G 6 8     4 1 7   2
H 7 2 3     9 1   4
I 4 1             6

Step 16

B2 is the last empty cell in box A1-C3 and the missing number is 9.

1 2 3 4 5 6 7 8 9
A 8 5 7       4 6 9
B 2 9 4 5     3 1 8
C 1 3 6 4     2 7 5
D     2 7     5    
E     8   3   6    
F     1     4      
G 6 8     4 1 7   2
H 7 2 3     9 1   4
I 4 1             6

Step 17

Because of the number 9 just placed, the only position in row C for another 9 is cell C5.

1 2 3 4 5 6 7 8 9
A 8 5 7       4 6 9
B 2 9 4 5     3 1 8
C 1 3 6 4 9   2 7 5
D     2 7     5    
E     8   3   6    
F     1     4      
G 6 8     4 1 7   2
H 7 2 3     9 1   4
I 4 1             6

Step 18

C6 is the last empty cell in row C and the missing number is 8.

1 2 3 4 5 6 7 8 9
A 8 5 7       4 6 9
B 2 9 4 5     3 1 8
C 1 3 6 4 9 8 2 7 5
D     2 7     5    
E     8   3   6    
F     1     4      
G 6 8     4 1 7   2
H 7 2 3     9 1   4
I 4 1             6

Step 19

Cell G4 can only contain the number 3 since all other numbers are somewhere in its row, column or box.

1 2 3 4 5 6 7 8 9
A 8 5 7       4 6 9
B 2 9 4 5     3 1 8
C 1 3 6 4 9 8 2 7 5
D     2 7     5    
E     8   3   6    
F     1     4      
G 6 8   3 4 1 7   2
H 7 2 3     9 1   4
I 4 1             6

Step 20

Because of the number 3 just placed, the only position in row I for another 3 is cell I8.

1 2 3 4 5 6 7 8 9
A 8 5 7       4 6 9
B 2 9 4 5     3 1 8
C 1 3 6 4 9 8 2 7 5
D     2 7     5    
E     8   3   6    
F     1     4      
G 6 8   3 4 1 7   2
H 7 2 3     9 1   4
I 4 1           3 6

Step 21

Because of the number 3 just placed, the only position in column 6 for another 3 is cell A6.

1 2 3 4 5 6 7 8 9
A 8 5 7     3 4 6 9
B 2 9 4 5     3 1 8
C 1 3 6 4 9 8 2 7 5
D     2 7     5    
E     8   3   6    
F     1     4      
G 6 8   3 4 1 7   2
H 7 2 3     9 1   4
I 4 1           3 6

Step 22

Cell D6 can only contain the number 6 since all other numbers are somewhere in its row, column or box.

1 2 3 4 5 6 7 8 9
A 8 5 7     3 4 6 9
B 2 9 4 5     3 1 8
C 1 3 6 4 9 8 2 7 5
D     2 7   6 5    
E     8   3   6    
F     1     4      
G 6 8   3 4 1 7   2
H 7 2 3     9 1   4
I 4 1           3 6

Step 23

Because of the number 6 just placed, the only position in row F for another 6 is cell F2.

1 2 3 4 5 6 7 8 9
A 8 5 7     3 4 6 9
B 2 9 4 5     3 1 8
C 1 3 6 4 9 8 2 7 5
D     2 7   6 5    
E     8   3   6    
F   6 1     4      
G 6 8   3 4 1 7   2
H 7 2 3     9 1   4
I 4 1           3 6

Step 24

The number 6 does not yet appear in row B. Due to other 6s on the grid, the only place it can go is cell B5.

1 2 3 4 5 6 7 8 9
A 8 5 7     3 4 6 9
B 2 9 4 5 6   3 1 8
C 1 3 6 4 9 8 2 7 5
D     2 7   6 5    
E     8   3   6    
F   6 1     4      
G 6 8   3 4 1 7   2
H 7 2 3     9 1   4
I 4 1           3 6

Step 25

Because of the number 6 just placed, the only position in column 4 for another 6 is cell H4.

1 2 3 4 5 6 7 8 9
A 8 5 7     3 4 6 9
B 2 9 4 5 6   3 1 8
C 1 3 6 4 9 8 2 7 5
D     2 7   6 5    
E     8   3   6    
F   6 1     4      
G 6 8   3 4 1 7   2
H 7 2 3 6   9 1   4
I 4 1           3 6

Step 26

B6 is the last empty cell in row B and the missing number is 7.

1 2 3 4 5 6 7 8 9
A 8 5 7     3 4 6 9
B 2 9 4 5 6 7 3 1 8
C 1 3 6 4 9 8 2 7 5
D     2 7   6 5    
E     8   3   6    
F   6 1     4      
G 6 8   3 4 1 7   2
H 7 2 3 6   9 1   4
I 4 1           3 6

Step 27

Because of the number 7 just placed, the only position in column 5 for another 7 is cell I5.

1 2 3 4 5 6 7 8 9
A 8 5 7     3 4 6 9
B 2 9 4 5 6 7 3 1 8
C 1 3 6 4 9 8 2 7 5
D     2 7   6 5    
E     8   3   6    
F   6 1     4      
G 6 8   3 4 1 7   2
H 7 2 3 6   9 1   4
I 4 1     7     3 6

Step 28

The number 7 does not yet appear in column 2. Due to other 7s on the grid, the only place it can go is cell E2.

1 2 3 4 5 6 7 8 9
A 8 5 7     3 4 6 9
B 2 9 4 5 6 7 3 1 8
C 1 3 6 4 9 8 2 7 5
D     2 7   6 5    
E   7 8   3   6    
F   6 1     4      
G 6 8   3 4 1 7   2
H 7 2 3 6   9 1   4
I 4 1     7     3 6

Step 29

Because of the number 7 just placed, the only position in row F for another 7 is cell F9.

1 2 3 4 5 6 7 8 9
A 8 5 7     3 4 6 9
B 2 9 4 5 6 7 3 1 8
C 1 3 6 4 9 8 2 7 5
D     2 7   6 5    
E   7 8   3   6    
F   6 1     4     7
G 6 8   3 4 1 7   2
H 7 2 3 6   9 1   4
I 4 1     7     3 6

Step 30

D2 is the last empty cell in column 2 and the missing number is 4.

1 2 3 4 5 6 7 8 9
A 8 5 7     3 4 6 9
B 2 9 4 5 6 7 3 1 8
C 1 3 6 4 9 8 2 7 5
D   4 2 7   6 5    
E   7 8   3   6    
F   6 1     4     7
G 6 8   3 4 1 7   2
H 7 2 3 6   9 1   4
I 4 1     7     3 6

Step 31

Because of the number 4 just placed, the only position in row E for another 4 is cell E8.

1 2 3 4 5 6 7 8 9
A 8 5 7     3 4 6 9
B 2 9 4 5 6 7 3 1 8
C 1 3 6 4 9 8 2 7 5
D   4 2 7   6 5    
E   7 8   3   6 4  
F   6 1     4     7
G 6 8   3 4 1 7   2
H 7 2 3 6   9 1   4
I 4 1     7     3 6

Step 32

The number 2 does not yet appear in column 8. Due to other 2s on the grid, the only place it can go is cell F8.

1 2 3 4 5 6 7 8 9
A 8 5 7     3 4 6 9
B 2 9 4 5 6 7 3 1 8
C 1 3 6 4 9 8 2 7 5
D   4 2 7   6 5    
E   7 8   3   6 4  
F   6 1     4   2 7
G 6 8   3 4 1 7   2
H 7 2 3 6   9 1   4
I 4 1     7     3 6

Step 33

The number 3 does not yet appear in column 9. Due to other 3s on the grid, the only place it can go is cell D9.

1 2 3 4 5 6 7 8 9
A 8 5 7     3 4 6 9
B 2 9 4 5 6 7 3 1 8
C 1 3 6 4 9 8 2 7 5
D   4 2 7   6 5   3
E   7 8   3   6 4  
F   6 1     4   2 7
G 6 8   3 4 1 7   2
H 7 2 3 6   9 1   4
I 4 1     7     3 6

Step 34

Because of the number 3 just placed, the only position in row F for another 3 is cell F1.

1 2 3 4 5 6 7 8 9
A 8 5 7     3 4 6 9
B 2 9 4 5 6 7 3 1 8
C 1 3 6 4 9 8 2 7 5
D   4 2 7   6 5   3
E   7 8   3   6 4  
F 3 6 1     4   2 7
G 6 8   3 4 1 7   2
H 7 2 3 6   9 1   4
I 4 1     7     3 6

Step 35

E9 is the last empty cell in column 9 and the missing number is 1.

1 2 3 4 5 6 7 8 9
A 8 5 7     3 4 6 9
B 2 9 4 5 6 7 3 1 8
C 1 3 6 4 9 8 2 7 5
D   4 2 7   6 5   3
E   7 8   3   6 4 1
F 3 6 1     4   2 7
G 6 8   3 4 1 7   2
H 7 2 3 6   9 1   4
I 4 1     7     3 6

Step 36

Because of the number 1 just placed, the only position in row D for another 1 is cell D5.

1 2 3 4 5 6 7 8 9
A 8 5 7     3 4 6 9
B 2 9 4 5 6 7 3 1 8
C 1 3 6 4 9 8 2 7 5
D   4 2 7 1 6 5   3
E   7 8   3   6 4 1
F 3 6 1     4   2 7
G 6 8   3 4 1 7   2
H 7 2 3 6   9 1   4
I 4 1     7     3 6

Step 37

Because of the number 1 just placed, the only position in column 4 for another 1 is cell A4.

1 2 3 4 5 6 7 8 9
A 8 5 7 1   3 4 6 9
B 2 9 4 5 6 7 3 1 8
C 1 3 6 4 9 8 2 7 5
D   4 2 7 1 6 5   3
E   7 8   3   6 4 1
F 3 6 1     4   2 7
G 6 8   3 4 1 7   2
H 7 2 3 6   9 1   4
I 4 1     7     3 6

Step 38

A5 is the last empty cell in box A4-C6 and the missing number is 2.

1 2 3 4 5 6 7 8 9
A 8 5 7 1 2 3 4 6 9
B 2 9 4 5 6 7 3 1 8
C 1 3 6 4 9 8 2 7 5
D   4 2 7 1 6 5   3
E   7 8   3   6 4 1
F 3 6 1     4   2 7
G 6 8   3 4 1 7   2
H 7 2 3 6   9 1   4
I 4 1     7     3 6

Step 39

The number 5 is missing from box D1-F3 and its only possible position is cell E1.

1 2 3 4 5 6 7 8 9
A 8 5 7 1 2 3 4 6 9
B 2 9 4 5 6 7 3 1 8
C 1 3 6 4 9 8 2 7 5
D   4 2 7 1 6 5   3
E 5 7 8   3   6 4 1
F 3 6 1     4   2 7
G 6 8   3 4 1 7   2
H 7 2 3 6   9 1   4
I 4 1     7     3 6

Step 40

Because of the number 5 just placed, the only position in row F for another 5 is cell F5.

1 2 3 4 5 6 7 8 9
A 8 5 7 1 2 3 4 6 9
B 2 9 4 5 6 7 3 1 8
C 1 3 6 4 9 8 2 7 5
D   4 2 7 1 6 5   3
E 5 7 8   3   6 4 1
F 3 6 1   5 4   2 7
G 6 8   3 4 1 7   2
H 7 2 3 6   9 1   4
I 4 1     7     3 6

Step 41

Because of the number 5 just placed, the only position in column 6 for another 5 is cell I6.

1 2 3 4 5 6 7 8 9
A 8 5 7 1 2 3 4 6 9
B 2 9 4 5 6 7 3 1 8
C 1 3 6 4 9 8 2 7 5
D   4 2 7 1 6 5   3
E 5 7 8   3   6 4 1
F 3 6 1   5 4   2 7
G 6 8   3 4 1 7   2
H 7 2 3 6   9 1   4
I 4 1     7 5   3 6

Step 42

Because of the number 5 just placed, the only position in column 3 for another 5 is cell G3.

1 2 3 4 5 6 7 8 9
A 8 5 7 1 2 3 4 6 9
B 2 9 4 5 6 7 3 1 8
C 1 3 6 4 9 8 2 7 5
D   4 2 7 1 6 5   3
E 5 7 8   3   6 4 1
F 3 6 1   5 4   2 7
G 6 8 5 3 4 1 7   2
H 7 2 3 6   9 1   4
I 4 1     7 5   3 6

Step 43

Because of the number 5 just placed, the only position in row H for another 5 is cell H8.

1 2 3 4 5 6 7 8 9
A 8 5 7 1 2 3 4 6 9
B 2 9 4 5 6 7 3 1 8
C 1 3 6 4 9 8 2 7 5
D   4 2 7 1 6 5   3
E 5 7 8   3   6 4 1
F 3 6 1   5 4   2 7
G 6 8 5 3 4 1 7   2
H 7 2 3 6   9 1 5 4
I 4 1     7 5   3 6

Step 44

D1 is the last empty cell in box D1-F3 and the missing number is 9.

1 2 3 4 5 6 7 8 9
A 8 5 7 1 2 3 4 6 9
B 2 9 4 5 6 7 3 1 8
C 1 3 6 4 9 8 2 7 5
D 9 4 2 7 1 6 5   3
E 5 7 8   3   6 4 1
F 3 6 1   5 4   2 7
G 6 8 5 3 4 1 7   2
H 7 2 3 6   9 1 5 4
I 4 1     7 5   3 6

Step 45

I3 is the last empty cell in column 3 and the missing number is 9.

1 2 3 4 5 6 7 8 9
A 8 5 7 1 2 3 4 6 9
B 2 9 4 5 6 7 3 1 8
C 1 3 6 4 9 8 2 7 5
D 9 4 2 7 1 6 5   3
E 5 7 8   3   6 4 1
F 3 6 1   5 4   2 7
G 6 8 5 3 4 1 7   2
H 7 2 3 6   9 1 5 4
I 4 1 9   7 5   3 6

Step 46

G8 is the last empty cell in row G and the missing number is 9.

1 2 3 4 5 6 7 8 9
A 8 5 7 1 2 3 4 6 9
B 2 9 4 5 6 7 3 1 8
C 1 3 6 4 9 8 2 7 5
D 9 4 2 7 1 6 5   3
E 5 7 8   3   6 4 1
F 3 6 1   5 4   2 7
G 6 8 5 3 4 1 7 9 2
H 7 2 3 6   9 1 5 4
I 4 1 9   7 5   3 6

Step 47

Because of the number 9 just placed, the only position in column 7 for another 9 is cell F7.

1 2 3 4 5 6 7 8 9
A 8 5 7 1 2 3 4 6 9
B 2 9 4 5 6 7 3 1 8
C 1 3 6 4 9 8 2 7 5
D 9 4 2 7 1 6 5   3
E 5 7 8   3   6 4 1
F 3 6 1   5 4 9 2 7
G 6 8 5 3 4 1 7 9 2
H 7 2 3 6   9 1 5 4
I 4 1 9   7 5   3 6

Step 48

Because of the number 9 just placed, the only position in row E for another 9 is cell E4.

1 2 3 4 5 6 7 8 9
A 8 5 7 1 2 3 4 6 9
B 2 9 4 5 6 7 3 1 8
C 1 3 6 4 9 8 2 7 5
D 9 4 2 7 1 6 5   3
E 5 7 8 9 3   6 4 1
F 3 6 1   5 4 9 2 7
G 6 8 5 3 4 1 7 9 2
H 7 2 3 6   9 1 5 4
I 4 1 9   7 5   3 6

Step 49

D8 is the last empty cell in box D7-F9 and the missing number is 8.

1 2 3 4 5 6 7 8 9
A 8 5 7 1 2 3 4 6 9
B 2 9 4 5 6 7 3 1 8
C 1 3 6 4 9 8 2 7 5
D 9 4 2 7 1 6 5 8 3
E 5 7 8 9 3   6 4 1
F 3 6 1   5 4 9 2 7
G 6 8 5 3 4 1 7 9 2
H 7 2 3 6   9 1 5 4
I 4 1 9   7 5   3 6

Step 50

F4 is the last empty cell in row F and the missing number is 8.

1 2 3 4 5 6 7 8 9
A 8 5 7 1 2 3 4 6 9
B 2 9 4 5 6 7 3 1 8
C 1 3 6 4 9 8 2 7 5
D 9 4 2 7 1 6 5 8 3
E 5 7 8 9 3   6 4 1
F 3 6 1 8 5 4 9 2 7
G 6 8 5 3 4 1 7 9 2
H 7 2 3 6   9 1 5 4
I 4 1 9   7 5   3 6

Step 51

H5 is the last empty cell in column 5 and the missing number is 8.

1 2 3 4 5 6 7 8 9
A 8 5 7 1 2 3 4 6 9
B 2 9 4 5 6 7 3 1 8
C 1 3 6 4 9 8 2 7 5
D 9 4 2 7 1 6 5 8 3
E 5 7 8 9 3   6 4 1
F 3 6 1 8 5 4 9 2 7
G 6 8 5 3 4 1 7 9 2
H 7 2 3 6 8 9 1 5 4
I 4 1 9   7 5   3 6

Step 52

Because of the number 8 just placed, the only position in row I for another 8 is cell I7.

1 2 3 4 5 6 7 8 9
A 8 5 7 1 2 3 4 6 9
B 2 9 4 5 6 7 3 1 8
C 1 3 6 4 9 8 2 7 5
D 9 4 2 7 1 6 5 8 3
E 5 7 8 9 3   6 4 1
F 3 6 1 8 5 4 9 2 7
G 6 8 5 3 4 1 7 9 2
H 7 2 3 6 8 9 1 5 4
I 4 1 9   7 5 8 3 6

Step 53

E6 is the last empty cell in box D4-F6 and the missing number is 2.

1 2 3 4 5 6 7 8 9
A 8 5 7 1 2 3 4 6 9
B 2 9 4 5 6 7 3 1 8
C 1 3 6 4 9 8 2 7 5
D 9 4 2 7 1 6 5 8 3
E 5 7 8 9 3 2 6 4 1
F 3 6 1 8 5 4 9 2 7
G 6 8 5 3 4 1 7 9 2
H 7 2 3 6 8 9 1 5 4
I 4 1 9   7 5 8 3 6

Step 54

I4 is the last empty cell in column 4 and the missing number is 2.

Congratulations - the puzzle is solved!

1 2 3 4 5 6 7 8 9
A 8 5 7 1 2 3 4 6 9
B 2 9 4 5 6 7 3 1 8
C 1 3 6 4 9 8 2 7 5
D 9 4 2 7 1 6 5 8 3
E 5 7 8 9 3 2 6 4 1
F 3 6 1 8 5 4 9 2 7
G 6 8 5 3 4 1 7 9 2
H 7 2 3 6 8 9 1 5 4
I 4 1 9 2 7 5 8 3 6
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