how many 5 inch recess cans do I need in a 12 by 8 kitchen
Also, what type of bulb are you going to use? What is the wattage limit on a 5" can? It's relative to the trim you're using. Open trims use the largest wattage bulbs and closed trims like eyeballs, use smaller wattage bulbs.
In the last few years, manufacturers have reduced the wattages you can put in these recessed lights. Open trim, 6" cans used to have a maximum capacity of 150 watts. If you look at the specs now, it's down to under 75 watts.