How to Build a Sudoku Generator in Excel with VBA

Step-by-step

You’ll build a 9×9 Sudoku grid that checks your answers as you type, plus a button that generates a brand-new puzzle. No VBA experience needed: the code is explained routine by routine, and the complete code is in the free download.

1. Turn on the Developer tab

Go to File > Options > Customize Ribbon, tick Developer and click OK.

2. Save as a macro-enabled workbook

Go to File > Save As and choose Excel Macro-Enabled Workbook (*.xlsm). Without this, Excel can’t keep the code.

3. Draw the grid

Rename Sheet1 to Puzzle. Select columns A:I and set the column width to 4. Select rows 1:9 and set the row height to 30, so the cells are square. Select A1:I9, centre the text horizontally and vertically, set the font to 16 and apply All Borders.

4. Add the thick 3×3 borders

Select the first block (A1:C3), open Borders > More Borders, choose a thick line and click Outline. Repeat for the other eight blocks.

5. Create the Solution sheet

Right-click the Puzzle tab, choose Move or Copy, tick Create a copy, move it to the end and rename the copy Solution. To test, type a sample puzzle into Puzzle (leave blanks empty) and its full solution into Solution.

6. Colour right and wrong answers

On Puzzle, select A1:I9 and go to Conditional Formatting > New Rule > Use a formula. For correct answers, use a light green fill:

=AND(A1<>"",A1=Solution!A1)

Add a second rule with a light red fill for wrong answers:

=AND(A1<>"",A1<>Solution!A1)

Type a number into a blank cell to test: it turns green if it matches the solution and red if not.

7. Add the VBA code

Press Alt+F11, right-click your workbook in the left panel and choose Insert > Module. Paste the code from the download. It’s made of a few short routines:

• NewRandomPuzzle: the main macro. It builds a full solution, copies it, removes 46 cells to make the puzzle, and writes both grids to the sheets. Change 46 to make puzzles easier (fewer blanks) or harder (more).
• FillGrid: fills the grid by backtracking. It tries numbers 1 to 9 in random order in the first empty cell, moves on if the number is allowed, and steps back when it hits a dead end.
• IsSafeVal: checks the Sudoku rules: the number can’t already be in the same row, column or 3×3 box.
• ShuffleArray: mixes up the numbers 1 to 9 (a Fisher-Yates shuffle), so every puzzle is different.
• FindEmpty, RemoveCells, CopyArray and WorksheetClearAndFill: small helpers that find the next blank, blank out random cells, copy the grid and write it to a sheet without touching the formatting.

8. Add the New Puzzle button

Press Alt+Q to go back to Excel. On Puzzle, go to Developer > Insert > Button (Form Control) and draw a button. Assign the NewRandomPuzzle macro and rename the button New Puzzle.

9. Play

Click New Puzzle: Excel clears the grid and lays down a fresh puzzle, with the answer hidden on the Solution sheet. Turn off gridlines on both sheets and save.