Finishing my basement and I need to calculate the number of can lights
needed to install in the drop ceiling. Dimensions are approx 21' x
22' and 7'7" high. I read one post recommending a can light every
4' and another every 6'. I want the space to be lit enough for work
space or food prep, but most of the time I intend to dim them down to
reading, PC, or TV watching levels.

Any suggestions on how to calculate the number and placement of cans ?

Thanks