Free Number Concentration Grid Table Game

Choose your size (9 to 225 squares in the grids)

script by Hilary Caws-Elwitt

as recommended in chapter 7 of The Non-Runner's Marathon Trainer by Whitsett, Dolgener, and Kole.



How many rows?       How many columns?      


I spent way too much time writing this back in 2004 (I didn't know Javascript), so I'd love to hear from anyone who uses this! View source to see the script. Please email me at

As of 2019 there are quite a few competitor sites out there... this was the first! Note that you can play online, and also print as many randomized concentration grids as you want, at no charge. To print, just click to start and then File/Print, right-click/Print, or whatever method works to print the resulting page.