At first glance I'd say 190. A 12x12 tile is 1 square foot. However, that would be assuming that the room dimensions are in whole feet, say 10 feet x 19 feet. Probably that is not the case. For instance if the room is 10'-4" x 18'-5" or some fractional portion of a foot on each side you would be cutting tiles and that would require more pieces. Take a sheet of graph paper and try sketching the room out to scale, then count the squares on the graph paper. Count each partial square as a whole tile. That should get you close. Then take into consideration that the first few tiles you cut will shatter until you get the hang of it and buy a few extra. Happy tiling! You will be an old pro by the time you finish. :-)