You have arrived at Nadine & Henry's Calcudoku solver page, rewritten from scratch in September 2025. This new version is easier to use, faster, smaller, and has more whitening and brightening power than the last version, which I wrote back in 2019. You should be able to enter the regions and the values much more quickly, with much less clicking.
  1. Select the type of the puzzle
  2. Select the size of the puzzle
  3. Change the upper and lower limits if needed
  4. Click in a cell to start defining your region
  5. Drag the mouse over the cells in the region
  6. Double click on the last cell of the region
  7. Repeat 3,4,5 until all regions have been defined
  8. If you make a mistake, click on "Delete a Region"
  9. And click anywhere in the region you want to delete
  10. When all the regions have been defined, an operator/value form appears below the puzzle
  11. The region for the operator/value will be highlighted
  12. Enter the operator and value for that region
  13. For example "6+" "2/" "-12-" "3 and" "15o" (no quotes)
  14. Repeat until all the regions have operators and values
  15. If you spot any mistakes, delete the region and try again
  16. When you are done, click on Solve Puzzle
  17. Don't blink, the solution should appear almost instantly
It really is that easy. Now for the bad news. If you enter a puzzle that can't be solved, chances are you made a mistake in the entry process. I can't really tell you where the mistake was made, you will have to carefully compare the what you entered with the original puzzle. When you find your error, just delete the errant regions and try again.
I have tried to be as permissive about what you enter for a value as possible. I expect a number followed by an operator. The number can have a leading "-" sign, if you want a negative number. The available operators are:
  1. + addition
  2. - subtraction
  3. * multiplication
  4. / division
  5. = identity, fixes the value
  6. ^ power, 2^3 = 8
  7. % modulo, 5 % 3 = 2
  8. and bitwise and, 3 and 5 = 1
  9. or bitwise or, 3 or 5 = 7
  10. empty no constraint on this region
You only need the first character for the and / or operators, so 3a and 2o are valid. Also, if you do not add an operator, addition is assumed. So 123 becomes 123+;
If you are entering a sudoku puzzle, the procedure is slightly different, and actually simpler. Just click on the cells that have values, and when you are done, click on the "Enter Values" button. The cell that is blinking will contain the value you are to provide.

Quote of the day:
Never try to teach a pig to sing; it wastes your time; and it annoys the pig

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