Short answer: What makes a good large-print sudoku?
Big starting numbers, one puzzle per page, bold black print on matte paper, and levels set by the solving methods needed, so you never have to guess. APH VisionAware calls 18 point the standard large-print size. Answers should be large print too. Enjoy it as a pastime: NIA says brain-game claims lack strong evidence.
Newsstand sudoku is often printed so small that the hard part is reading the grid, not solving it. And a puzzle labeled "easy" can turn out to need a trick nobody explained. You can check for both problems before you print or buy a book.
How big should the numbers be in large-print sudoku?
APH VisionAware says 18 point is the standard size for large print, and that bold black print on a matte white or cream background is easiest to read (APH VisionAware: Reading with Low Vision). A sudoku grid needs more room than a line of text, because the solver also writes small pencil notes in each square. Look for:
Starting numbers well above 18 point. One puzzle per page leaves room for numbers around 30 to 36 point.
Thick lines around each 3 by 3 box and thinner lines inside, so the boxes stand out at a glance.
Squares big enough for pencil notes, at least about two thirds of an inch across.
Instructions and answers in large print too. A tiny answer key undoes the point of a big grid.
How do sudoku difficulty levels actually work?
Every sudoku follows the same rule: fill the grid so each row, each column and each 3 by 3 box holds the digits 1 to 9 once. What changes between levels is the method you need to find the next number.
Easy and Medium can be solved with "singles": a square where only one digit fits, or a digit that fits in only one square of a row, column or box. Medium puzzles usually start with fewer numbers, so the singles take longer to spot.
Hard puzzles need a step such as "pointing" (a digit in a box is limited to one row, so you can remove it from the rest of that row) or "pairs" (two squares that can only hold the same two digits).
Very Hard puzzles need an advanced pattern such as a triple, an X-wing or an XY-wing.
A well-made puzzle has exactly one solution and can be finished by logic alone. If a book's "hard" puzzles make you guess and erase, the levels were probably set by counting starting numbers rather than by the methods needed.
Which level should a new or returning solver start with?
Start Easy, even for a strong solver who is new to sudoku. The first goal is learning to scan rows, columns and boxes.
Move up after three or four puzzles in a row feel comfortable. Stay at a level as long as it is fun.
Pencil and a good eraser beat pen. Write possible digits small in a corner, then erase as you rule them out.
Good light matters as much as print size. APH VisionAware suggests direct light focused on the page, and for most people with low vision a bulb under 5,000 K.
Solve together. One person reads out a row, the other looks for the missing digit. It works well on a visit or a quiet afternoon.
Will doing sudoku keep your memory sharp?
Nobody can promise that. The National Institute on Aging says some structured cognitive training has shown benefits in research, but warns there is not enough evidence that commercial brain-training games have the same effect (NIA: Cognitive Health and Older Adults). Enjoy sudoku as a pastime, and be wary of any puzzle book that claims to improve memory or prevent dementia.
How do you print sudoku so it stays large?
Print at "Actual size" or 100%. "Fit to page" can shrink a page meant to be read large.
Print only the pages you need. Choose a page range in the print dialog, so one level at a time goes on the table.
Matte paper, not glossy, cuts glare. Plain copy paper works.
Keep the answer pages apart in a folder, so a quick look at one answer does not spoil the next puzzle.
Where can you try large-print sudoku for free?
Our Free Large Print Sudoku Sampler has 10 puzzles, one per page, from easy to very hard, with answers. It's a PDF with no sign-up.
If you want a bigger stack ready to print: Slow Coffee Sudoku is a 280-page US Letter PDF with 300 puzzles: 80 Easy, 90 Medium, 85 Hard and 45 Very Hard. The first 100 are one per page with 36 point starting numbers, the next 200 are two per page at 22 point, and nothing in the file is smaller than 16 point. A computer solver set each level by the methods it needs, and a second solver checked that every puzzle has exactly one solution. Answers for all 300 are included. It's licensed for printing at home. $4.99 on Gumroad or Etsy.
General information. Sudoku is a puzzle for enjoyment. It is not a medical product and does not diagnose, treat or prevent any condition. Talk to an eye doctor or low-vision specialist about your own vision.