An example 25×25 Sudoku: twenty-five symbols fill every row, column and 5×5 box (a few 1-9 shown).
25×25 Sudoku is one of the largest formats in common use: a twenty-five-by-twenty-five grid divided into 5×5 boxes, filled with twenty-five different symbols - usually the numbers 1-25 or the letters A-Y. Each row, column and box must hold all twenty-five once. It is a marathon, and it rewards patience far more than cleverness.
The rule: twenty-five symbols per row, column and 5×5 box
Fill the grid so every row, every column and every 5×5 box contains all twenty-five symbols exactly once. A single 5×5 box already holds a complete set - below, one box is filled with 1 through 25 to show the range.
One 5×5 box holds all twenty-five symbols (1-25). The full grid has twenty-five such boxes.
Patience over difficulty
A 25×25 is not harder in principle than a 9×9 - the techniques are the same - but the scale is enormous: 625 cells, twenty-five candidates each, and boxes five wide. Careful, complete pencil-marking is not optional; a single missed elimination is very easy to make and painfully slow to find. Approach it as a long, calm project, working steadily one unit at a time.
Numbers or letters
Puzzles for a general audience use 1-25, which is unambiguous but makes most cells two characters wide. Others use the letters A-Y, keeping every cell a single character. The logic is identical either way - the symbols are just labels for twenty-five distinct values.
Solving strategy
- Pencil-mark everything. With twenty-five possibilities per cell, thorough notes are the only way to stay on track.
- Work box by box. Finish one 5×5 box before moving on, to avoid losing your place.
- Hunt hidden singles per symbol. Take one symbol at a time and place it wherever it is confined to a single cell.
- Use the same techniques as 9×9. Naked pairs, hidden singles and X-Wings all scale up unchanged.
Common mistakes
- Sloppy candidate marks. On a grid this vast, one wrong mark can waste hours.
- Forgetting a symbol. All twenty-five must appear - it is easy to overlook one when scanning.
- Mixing labelling schemes. Decide whether the grid uses 1-25 or A-Y and stick with it.
- Rushing. The 25×25 is a test of stamina and care, not speed.
Can I play it here?
Not yet - Sudoku 25×25 isn't one of the puzzle types SudokuStreak generates for now. But you can learn its rules above, and there's plenty here to sink your teeth into meanwhile:
- Try the closely related Classic, which you can play right now.
- Browse all the Sudoku variants we do offer.
- Or print free puzzles from the printable PDF page.
Where to play it
Sudoku 25×25 belongs to the size variant family and runs on 25×25. It is not one SudokuStreak generates yet - but the deduction it trains is the deduction every Sudoku runs on.
Difficulty and type are two separate dials here: the type sets the extra rule, the level sets how much of the grid you start with. Expert Sudoku leaves 25 of the 81 cells filled, where the beginner tools dry up almost entirely; Evil Sudoku leaves 23, with no easy moves at all. Take it at the gentler end while the pattern is still new, and move up once it stops being a fight.